Stratigraphy of Middle Tertiary Rocks in Part of West-Central … · 2011. 6. 27. · Stratigraphy...
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Stratigraphy of Middle Tertiary Rocks in Part of West-Central Florida
GEOLOGICAL SURVEY BULLETIN 1092
This report concerns work done on behalf of the U.S. Atomic Energy Commission and is published with the permission of the Commission
Stratigraphy of Middle Tertiary Rocks in Part of West-Central FloridaBy WILFRED J. CARR and DOUGLAS C. ALVERSON
GEOLOGICAL SURVEY BULLETIN 1092
_This report concerns work done on behalf of the U.S. Atomic Energy Commission and is published with the permission of the Commission
UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1959
UNITED STATES DEPARTMENT OF THE INTERIOR
FRED A. SEATON, Secretary
GEOLOGICAL SURVEY
Thomas B. Nolan, Director
The U.S. Geological Survey Library has cataloged this publication as follows:
Carr, Wilfred James, 1926-Stratigraj)hy of middle Tertiary rocks in part of west-
central Florida, by Wilfred J. Carr and Douglas C. Alver- son. Washington, U.S. Govt. Print. Off., 1959.
iv, 112 p. maps (3 fold, in pocket) diagrs., tables. 25 cm. (U.S. Geological Survey. Bulletin 1092)
This report concerns work done on behalf of the U.S. Atomic Energy Commission and is published with the permission of the Commission.
Bibliography: p. 69-71.1. Geology Florida. 2. Geology, Stratigraphic Tertiary. 3. Bor
ings Florida. i. Alverson, Douglas Creighton, 1931- joint author, n. Title. (Series)
[QE75.B9 no. 1092] G S 59-231
For sale by the Superintendent of Documents, U.S. Government Printing Office Washington 25, D.C. Price $1.25 (paper cover)
Abstract..:_ _ __._-_.___..__-_-__-_____------__-___-..-..--_--_--___- 1Introduction._-_________-_-___-__-__--__-___-----_...-_--,-_---__-- 2
Purpose and extent of work._-____-__--___---___-___-_---_------ 2Previous work.________________________________________________ 4Physiography __._.,___-.__. _________-_L ________________________ 4Acknowledgments _-___.._._______-__--______.___.,__-_____--____ 5
Laboratory work...____.____._______________-________________________ 5Procedures-..____--_.__.______.______.____.._______._-_______ 6Evaluation of results..____________________________..___^__-___._ 7
Stratigraphy. ____;__._____-______-_______-___-.._______-__ __________ 8Eocene rocks_-__-__-_-__-_.--_-____-__--________--__--_---___ 8
Ocala limestone.____,_--___---___-__-.__-_-__-_--_----_-_-_ 8Oligocene rocks___.____________________________._ _____--_____-_ 0
Suwannee limestone..._--__---___.______-_____,.._____-____ 91 Miocene rocks__ -_____.-..__._____..___;_..._.__.-__._____-__ 14
Tampa limestone.___-_-____--______-__--.____,_-___-______ 14Hawthorn formation._____._.._.____.______._._._____.__.__ 33
Post-middle Miocene rocks.____ ____________.:__-_____^_______. 48Bone Valley formation._._____._______.__,_____...____._.___ 48
x Undifferentiated Miocene and Pliocene rocks___._____.^_-_._ 49Weathering.__^_.._,_______.___ _.____....___.___..____.___.__._____ 50
Suwannee limestone___.-___-._-_-_-.^-_-_-_.-___--_--._--_-- 51Tampa limestone..-______--__-__-___-_._-_.-_____.-_-_-__.__-_ 51Hawthorn formation.____________________v-----_-_----------_-- 54Post-middle Miocene rocks.--_-_______-_--____-____--____^_-___ 55Date of weathering.________.____________._______ __'.___.__.___.._ 55
Petrographic comparisons______.________________:__ __._____'-__-^-__ 56Geologic history.-__--__--__-_____-_._^.. T _ T _._--.-_.._._---______.__ 58
% Structure. __________-_____-__-____-_.__,:____________-_ _________ 58_0cala uplift and distribution of Miocene rocks___ _-___-___-___ 58Faulting. _i_._._-__.__________________L__j._ _______ _____ ____ 59
. Contact between the Tampa limestone and. the Hawthorn for-. mation____________.__________________________r_________ 60
.Structural features of Miocene rocks______.._________ _________ 62^ Sedimentation__ .______.______ ____________._^________^___.__'____ 63
Suwannee limestone____________ ___.__________-___-_-____ 63Tampa limestone. ____ ____- _ _.-_-__ __-___--_______----_---__ 63
t Hawthorn formation__________________________________.____ 64Sand and clay of the Miocene.__-___---_________--__--__-_-_ 65
Summary of geologic history.__,^_..__._____________________________ 66Economic geology.__--________--_________--_-______-_.--_______.__ 67
* Phosphate and uranium.________.__________________ __________-_ 67Limestone and dolomite._-_____---_.__-_____._______--_-_-_---- 68
"* Literature cited_________.________________________________________ 69Exposures of the Suwannee and Tampa limestones and the Hawthorn for
mation. ________________________________________________________ 72Lithologic logs of core holes__-...-__-__-________._____-___--._____-_ 91Index._...__..__._..._.._.._....___._______.__.........___._.____ Ill
* ni
IV CONTENTS
ILLUSTRATIONS
[Plates are in pocket]
PIRATE 1. Geologic map and sections of parts of Hillsborough, Pasco, and Polk Counties, Florida
2. Map of west-central Florida showing location of sections, test holes, and outcrops - --- -
3. Map of west-central Florida showing structure contours on the base of the Hawthorn formation and the thickness of the Tampalimestone
............... . . PageFIGURE 1. Index .map of peninsular Florida____________..___--__-___ 3
-2. Sections through core holes in Hillsborough County. _______ 11- 3. Section through core holes in Polk and Pasco Counties ._-__,. 14
4. Typical cumulative curves of sand for Ocala, Suwannee, and-Tampa limestones and Hawthorn formation________.^_^ 15 ;
5. Frequency distribution of fifth percentile value and sorting > coefficient in samples of Suwannee and Tampa limestones and Hawthorn formation______________________________ 16 !
6. Frequency distribution of median diameter, percent sand, and » percent total insoluble material in samples of Suwannee and Tampa limestones and Hawthorn formation __________ 17
- 7. Petrographic and lithologic log of Davison Chemical Corp.churn-drilled well, Polk County____^________-_____-__-_ 18
8. Ranges of petrographic characters of formations in Davison ^ Chemical Corp. well, Polk County_________-__________ 19
9. -Ternary diagram of soluble and insoluble constituents oflimestone samples^_^_^----__-----------_--__---__---_- 20
10. Sketch map and section of Tampa limestone at locality 26___ 22 -}11. Diagram showing the relation between the four divisions of
the Hawthorn formation;__;_____.____________________ 3412. Diagrammatic sketch showing stratigraphic relations at lo
cality 83___ - _-----______-______-______ 41 113. Diagrammatic sketch showing stratigraphic relations at ^
locality 13____._______________________ 4214. Diagrammatic sketch showing stratigraphic relations at lo
cality 24____________________________ 4515. Diagrammatic sketch showing stratigraphic relations at lo
cality 6______________________________ 4616. Sections through core holes in Hillsborough County. _____ 47
TABLES
Page TABLE 1. Distribution of fossils in the Suwannee limestone._____-___--_ 12
2. Distribution of fossils in the Tampa limestone_______-_ __-- 263. Distribution of fossils in the Hawthorn formation___________ 374. Summary of medians of petrographic characteristics._________ 57
STRATIGRAPHY OF MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
By WILFRED J. GARB and DOUGLAS C. ALVERSON
ABSTRACT
Petrographic studies of the Suwannee limestone (Oligocene), Tampa limestone (lower Miocene), and Hawthorn formation (middle Miocene) yielded data that are useful for correlation in a region where weathering has thoroughly altered, the rocks. Mechanical analysis of sand aided in the recognition of formations in weathered exposures. An efficient laboratory method for insoluble-residue and mechanical analysis of sand was developed. Preliminary work indicates that the kind and distribution of heavy minerals, clay minerals, and chert should also be valuable in any further stratigraphic studies of this area.
Mapping of rocks of Oligocene and Miocene age in Hillsborough, Pasco, and Polk Counties has extended the known limits of the Tampa limestone northeast ward; some of the sand and clay previously mapped.as Hawthorn formation in northeastern Pasco County belongs to the Tampa. Sand of the Hawthorn formation is coarser than that of the Tampa, limestone. Although phosphate nodules are not normally present in the Tampa, they are abundant in places, particularly in Polk County. A contact between calcareous and noncalcareousparts of the Hawthorn was mapped in northern Hillsborough and Polk Counties. More than 50 new localities were examined. . .
Structure contours on the base of the Hawthorn formation, and other evidence from well logs and surface exposures suggest an unconformity between the Tampa limestone and Hawthorn formation. A fault that brings rocks of Eocene age adjacent to the Suwannee and Tampa limestones is believed present in north western Polk County. The Suwannee limestone appears to be absent east of this structure. . .-.. - .
Weathering in this part of Florida results in local concentration of iron, phos phorus, alumina, and silica. Secondary chert and aluminum phosphate zones form where the parent material is favorable. Leaching forms a weathering profile of increasing solubility downwards, which typically contains,. from top to bottom, quartz sand, iron-stained clayey sand with chert'and iron and phos- phatic hardpans, blue-green sandy clay with local calcium phosphate nodules, and a thin zone of slightly calcareous clay passing abruptly into limestone. The presence of a substantial amount of secondary chert in a weathered section .is believed to be evidence that limestone was formerly present. Crenulated bedding, common in weathered exposures in the area, is probably a result of solution of limestone and differential settling of the residue. The presence of weathering products such as chert and aluminum phosphate below beds of virtually unleached limestone suggests periods of intraformational weathering.. "
Zones consisting of material weathered from; the Suwannee limestone are relatively thin and nonphosphatic, and there is a high proportion of clay to sand
1
2 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
and much chert. Material weathered from the Tampa limestone typically shows local silicification and contortion of bedding, and contains clayey residues that are generally low in phosphate. Residue of the Hawthorn formation is commonly phosphatic, lacks chert, and contains a few quartz sand grains that are conspicu ously coarser than normal.
Fauna and petrography suggest a shifting lagoonal, insular, and locally fresh water environment of deposition for the Tampa limestone. Open sea and relatively static conditions of sedimentation characterized Hawthorn time. The rather abrupt change in conditions of deposition from Oligocene to Miocene time, which resulted in an increase in amount and grain size of clastic material in rocks of Miocene age, can be ascribed to currents carrying material into the Florida peninsula from sources to the north, and possibly to ash falls from distant volcanic activity. The period of major weathering in the area probably took place in late Pliocene or early Pleistocene, but evidence of periods of older weathering is believed to be present.
Prolonged leaching of zones rich in calcium phosphate (apatite) produces in some areas a hardpan ("leached zone") that consists chiefly of relatively insoluble aluminum phosphate minerals (wavellite, pseudowavellite, and others) that commonly retain small amounts of uranium. In northeastern Hillsborough County, north and west of the boundaries of the land-pebble phosphate deposits, a belt was found that contains zones of aluminum phosphate which resulted from leaching of phosphatic beds, chiefly of the Hawthorn formation. These zones generally have a thin overburden and a moderate uranium content. Phos phate or uranium is not present in commercial quantities in unleached limestone of this area, but the upper surface of limestone of the Hawthorn in the land-pebble phosphate" district was found to contain locally nearly 20 percent MgO.
INTRODUCTION
PURPOSE AND EXTENT OF WORK
This report presents the results of part of a geologic study of the phosphate deposits in central Florida. The area in Hillsborough and Polk Counties called the land-pebble phosphate district produces about three-fourths of the phosphate mined in the United States. The present investigation was begun in March 1953 by the U.S. Geological Survey on behalf of the U.S. Atomic Energy Commission. The ultimate objective of the work in Florida is to determine the geologic history of the phosphate deposits and associated sediments, hi order that the distribution of phosphate and uranium will be more clearly understood.
As a contribution to this objective we have studied the stratigraphy of the formations, chiefly limestone, which underlie (or are closely associated with) the land-pebble phosphate deposits of west-central Florida. The unconsolidated residue and sediments above the limestone received less detailed study. For this report work was concentrated on the northwestern fringes of the land-pebble district because this area contained the bulk of the exposures and seemed to be the most critical in the solution of stratigraphic problems. The area mapped (fig. 1) contains about 1,700 square miles in Hillsborough,
INTRODUCTION
Polk, and Pasco Counties. The Hawthorn formation of middle Miocene age, the Tampa limestone of early Miocene age, and the Suwannee limestone of Oligocene age were mapped and sampled in detail. Rocks older than Oligocene and younger than middle Miocene age were not extensively studied.
84
Area geologically mapped, Plate 1
Approximate boundary of tana-pebble phosphate district
Ocala uplift as shown by zero contour, top of Inglis member of Vernon (1951), Moodys Branch formation as used by Vernon (1951); modified from Vemon (1951, pi. 2)
FIGURE 1. Index map of peninsular Florida showing location of Ocala uplift, land-pebble phosphate district, and areas mapped and studied for this report.
4 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
To supplement surface observations holes were drilled with a power auger in critical areas, about 25 core holes drilled by a contractor were logged in detail, and well logs were studied.
Laboratory work, a "major portion of the study, consisted of in soluble-residue analysis of limestone samples, mechanical analysis of the residues, and subordinate study of heavy minerals. A number of thin sections of limestone, chert, and phosphatic material were examined. Spectrographic, chemical, and X-ray analyses were made by the Geological Survey laboratories;
The extensive laboratory work done for this study was prompted by the need for a uniform means of comparing and delimiting forma tions in a region where weathering and lithologic similarity of for mations, scarcity of fossils, and lack of good exposures have made mapping difficult.
PREVIOUS WORK
Geology of the area mapped for this report has not been studied previously in detail, although Mansfield (1937), Cooke (1945), and others have studied fossils or mapped the area on a small scale. Sellards (1915) and Matson (1915) described the Florida phosphate deposits. More recent work on the phosphate deposits has been summarized by Cathcart, Blade, Davidson, and Ketner (1953). Applin and Applin (1944, p. 1674-1677) give a summary of the important contributions to Florida stratigraphy.
PHYSIOGRAPHY
Central Florida has a subtropical climate, with a range of average monthly temperature from about 60° in January to about 80° in July. The yearly precipitation for the area mapped is a little over 50 inches, most of which falls from June through October.
Total relief in the area is about 250 feet from sea level to the hills near Dade City, Pasco County, and the ridge north and south of Lakeland, Polk County (pi. 1).
Most of west-central Florida is a sandy plain with minor depressions and ridges, which hi general trend north-northwest. The surface topography reflects in a subdued manner subsurface features of the limestone, modified in some areas by dunelike sand hills. There are several ill-defined belts of limestone solution depressions, sinkholes, and springs hi the area. One such belt trends northwest across central Hillsborough County. Small lakes or swamps fill most of the depres sions. Lakes are particularly numerous north of Tampa and in the Dade City and Lakeland highlands. Four rivers drain the mapped area: two of the rivers, the Hillsborough and the Alafia, flow westward into Hillsborough Bay and the Gulf of Mexico; the Peace Kiver begins
; .;'";; LABORATORY WORK ' : !.::. .; 5
southeast of Lakeland and flows southward out of the area; the Withlacoochee River rises in northern Polk County and flows west and north out of the area. These rivers are sluggish, swamp-bordered streams which have few rapids and are subject to reversal of flow by tides for distances of .5-10 miles from their mouths. In most places the rivers flow on limestone or cher4t bedrock. Only 9 feet of section is exposed at the, thickest limestone outcrop in the mapped area. In most of the area the limestone bedrock is covered by 30-50 feel; of unconsolidated sand and clay. ; .
ACKNOWLEDGMENTS
We gratefully acknowledge the assistance of F. S. MacNeil of the U.S. Geological Survey for his identification of fossils and suggestions on the basic stratigraphic problems. J. W. Wells of the U.S. Geo logical Survey identified several coral specimens. C. B. Hunt, J. T. Hack, and all the members of the Southeastern Coastal Plains projects of the U.S. Geological Survey have contributed to an understanding of the geology of central Florida.
Analytical work was done by the U.S. Geological Survey: W. F. Outerbridge and R. G. Petersen made the X-ray analyses; Ivan Bar low, . Harry Levine, Roberta Smith, Wendell Tucker, and Maryse Delevaux made the chemical analyses; Julius Goode and Benjamin McCall, the radiometric analyses; and H..W. Worthing and Joseph Haffty made the spectrographic analyses.
Special thanks are due to the members of the Florida Geological Survey, Dr. Herman Gunter, director, for supplying well logs from
-, their files. .LABORATORY WORK
This investigation presented special problems in stratigraphic correlation, chiefly because of (1) scarcity and small size of outcrops and then- uneven geographic distribution, (2) lithologic similarity of the formations, (3) difficulty of locating the vertical position of exposures within formations, (4) intensity of weathering and similarity of residues, and (5) unconsolidated nature of many of the rocks.
A laboratory procedure was therefore developed to process a large number of samples in order to obtain sufficient data for valid correla tion of formations. Quartz sand and heavy minerals are the most stable components of these rocks. Under the influence of weathering all other constituents carbonate, clay, phosphate are subject to change in relative amount and composition. Accordingly, methods .of insoluble-residue and mechanical analysis were employed in the laboratory. The Wentworth (1922) grade scale was used throughout the work.
6 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
PROCEDURES
After experimentation the following laboratory procedures were found to be the most practical. The calcareous rocks were broken until most of the pieces were 2 or 3 cm (centimeter) in diameter. Enough crushed rock was used to provide at least 5 g (gram) of sand residue. The weighed sample was dissolved in a 4,000 ml (milliliter) Pyrex beaker by half-strength hydrochloric acid. The sample was left in the acid for at least 16 hours. Washing and decantation were repeated until the acidity was low.
The wet residue was washed into the jar of an electric food blender. This type of mixer was found to be superior to the "milkshake" blender often used in sedimentary laboratories. The agitator re volves at very high speed and has large sharp blades at the bottom of the container. Four minutes of agitation hi the blender was.found to be ample. In the few cases when a sample did not disaggregate completely in the blender the clayey lumps were carefully crushed with a rubber soil pestle.
After disaggregation the samples were washed through a U.S. Standard 230-mesh screen in order to separate sand from clay and silt. Time did not permit size studies of the clay and silt fractions, but the total amount of fine material was determined by drying and weighing. Sand fractions were dried in evaporating dishes, weighed, and screened with a mechanical shaker. The coarser particles of impurities such as chert and aluminum phosphate minerals in the sand samples were screened out, hand sorted, and the percentage of the remaining finer impurities estimated, but those samples which contained too much foreign material were not used in size studies.
Noncalcareous samples consisted of quartz sand, silt, and clay; they were mostly unconsolidated and were easily disaggregated in the blender. The sand fractions of samples that contained calcium phosphate nodules were treated with full-strength hydrochloric acid, and the dissolved phosphate considered part of the clay fractions for purposes of uniformity. Most of the calcareous samples contained negligible amounts of phosphate nodules.
All the sand fractions were screened with a mechanical shaker for 5 minutes. U.S. Standard 20-, 30-, 40-, 50-, 70-, 100-, 140-, 200-, and 230-mesh screens were used. Weights of screen fractions were ob tained by accumulative weighing. Later all +100-mesh material from each sample was combined for heavy-mineral study. The weight percentages of the sand were plotted on cumulative curves as 100 percent of the sample; and median diameter, Trask (1932, p.
71-72) sorting. coefficient, and fifth percentile values *'were deter mined from the curves.
About 10 representative samples from the +100-mesh fraction of each formation were separated with bromoform and the heavy minerals identified.
EVALUATION OF RESULTS
There are several sources of possible error in the laboratory methods, such as loss of clay in decantation and in acidulation, attrition of sand, and errors in weighing. Only the latter two factors influence the median diameter, sorting coefficient, and fifth percentile .yalues of the cumulative curves.
Care was taken to prevent loss of clay in decantation by allowing plenty of settling time. Grim, Dietz, and Bradley '(1949, p.. 1788) found that acidulation did not remove a significant amount of alumi num and silicon from residues. In order to test the effects of attrition in the blender, a sample of sand was mechanically analyzed before' and after agitation in the blender for 8 minutes, twice the normal tune. The sand lost only 3% percent of its weight and was reduced only 0.001 mm in median diameter.
To check the reliability of the insoluble-residue method and the consistency of lithology within samples, 2 splits each of 29 samples were dissolved and total insoluble material measured. The maximum" difference between percent of total insoluble residue in the first and second determinations was 8.2. The: average difference was 2.7, a reasonably small variation. .
It should be emphasized that the objective of the laboratory work was to compare.uniformly obtained data on samples of known age and formation rather than absolute values for individual samples.
In heavy-mineral analysis, it was found that solution of 100-300 g of limestone was necessary to provide 100 grains of heavy minerals,- and not enough samples could be examined in the time available to permit strict comparisons of formations. However, the small amount of data obtained disclosed some mineralogical differences which, when used with other information, were helpful in reaching a decision on doubtful samples and outcrops.
Some of the illustrations which accompany this report show the kind of comparisons that may be made with (the data. Although there is considerable overlap in characteristics, there is a definite
> The fifth percentlle value or Ft is obtained from the cumulative, curve, and is a sensitive measure of the proportionate amount of "coarse" sand in a sample. A Ft of 0.15 means that 6 percent of the sand in the sample Is as coarse, or coarser than, 0.15 mm. . ,
8 MIDDLE TERTIARY ROCKS IN TART OF WEST-CENTRAL FLORIDA
pfogriession in data from one formation to another, indicating that at any particular point a vertical section through the formations will be characterizied by shifts in petrographic values at formational boundaries. - '- "
STRATIGRAPHY .....' ;
.EOCENE BOCKS
OCAI/A LIMESTONE
Previous work. Ball and Harris (1892, p. 103) first used the name Ocala to include limestone exposed hi quarries near Ocala hi Marion, County, Fla. They correlated the Ocala limestone with rocks which they then regarded as Eocene hi age. Matson and Sanford (1913, p. 70) placed the Ocala limestone hi the Oligocene, but Cooke (1915) proved that it is of Jackson (late Eocene) age and that it underlies Vicksburg. Applin and Applin (1944, p. 1683-1684) recognized a twofold faunal division of the formation. Vernon (1951, p. Ill) restricted the name Ocala to the upper part of the formation and correlated the lower part with the Moodys Branch formation of Alabama and Mississippi. On the basis of faunal zones Vernon (1951, p. 115) proposed his names Inglis and Williston for the lower and upper members respectively of the Moodys Branch formation as exposed hi Citrus and Levy Counties hi Florida. Vernon (1951, pi. 2) used the top of. his Inglis member, a conformable surface, in his structural studies of northern peninsular Florida. Puri (1953a, p. 130) proposed that all sediments of Jackson age in Florida be called the Ocala group. He suggested a new name, Crystal River formation, for Vernon's Ocala limestone (restricted), and suggested raising Vernon's Inglis and Williston to formational status. He also listed distinctive faunizones for these formations.
Age and extent. The Ocala limestone is late Eocene hi age and is correlated with the Jackson group hi Alabama (MacNeil, 1947). In this report Ocala is retained-'for all rocks of late Eocene age hi west- central Florida. The Ocala limestone is locally exposed hi a belt that runs from Lafayette County on the northwest to northern Pasco and Polk Counties on the southeast. It is present in the subsurface over much of northern and probably southern peninsular Florida, but is missing from many scattered wells hi the central part of the peninsula. ,The average thickness of the formation is about 150 feet, but it is over 300 feet thick in wells in southern Polk County.
General lithology. TheOc&l&ia a pure massive marine white to tan granular limestone^ which is locally a porous friable coquinalike mass of Foraminifera and mollusks in a chalky or pasty carbonate matrix. Solution pipes filled with clay and large irregular masses of chert are common locally. A summary of petrographic data for the Ocala
STRATIGRAPHY., :.. ' . 1 -.9
limestone is given in table 4. Details of Ocala petrology have been studied by Fischer (1949, p. 41-70), ...
'Stratigraphic relations. The Ocala lies unconformably upon the Avon Park, Lake City, and Tallahassee limestones (Cooke, 1945, p.
.56) and is overlain unconformably by all formations in contact with its top. . '.',..
Fauna. Large miliolid and camerinid Foraminifera are very abundant in, and characteristic of, the Ocala limestone. Echinoid» are abundant, particularly in the lower part. Mollusks, including' pectens and turritellid gastropods, are also abundant, but not as conspicuous as in the later formations.
OLIQOCENE ROCKS
SUWANNEE LIMESTONE
GENERAL FEATURES
Previous work. Cooke and Mansfield (1936, p. 71) proposed the name Suwannee for limestone of late Oligocene age exposed along the Suwannee River in northern Florida. Previously Matson and Clapp (1909, p. 73) had referred these rocks to the Hawthorn formation, and Mossom (1925, p. 73-77; 1926, p. 81-82) correlated them with the Glendon limestone, now considered a member of the Byram forma tion in Alabama (MacNeil, 1944, fig. 1). Cooke and Mossom (1929,.p. 89-91) had included the present Suwannee limestone in the Tampa limestone, which was then thought to be Oligocene in age. Vaughan (1910, p. 155) recognized the absence of Oligocene rocks from an area in east-central Florida. The Applins (1944, p. 1681) divided .the Oligocene into two faunal units in northern Florida, the, upper of which is much more extensive and is correlated with the Suwannee limestone. In northwestern Florida MacNeil (1944, p. 1316) re stricted the Vicksburg group to the middle Oligocene, namely the Marianna limestone and the Byram formation. The Suwannee
'limestone is now considered by MacNeil (1946, p. 55) to be equivalent to the Byram and Chickasawhay formations combined.
Age and extent. The Suwannee limestone is late Oligocene in age. As used in this report it includes all sediments of Oligocene age in west-central Florida. The formation is locally exposed in north western peninsular Florida. Limestone typical of the Suwannee limestone crops put along the upper Suwannee River. It is also exposed locally in southern Citrus and Sumter Counties, most.of Hernando County, northwestern and eastern Pasco County, the
'northeast corner of Hillsborough County, and the northwest corner of Polk County. In the subsurface the Suwannee extends to southern Florida, but it is missing from east-central peninsular Florida. In the area mapped the formation averages 150 feet thick; it is missing
10 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
in eastern Polk County, but is about 300 feet thick near the gulf coast.The best exposure of the Suwannee limestone visited by us in this
area is at locality 62 (see pi. 2 for localities) in Pasco County. Fairly good exposures are also present at localities 67 and 70.
General lithology. The Suwannee is a pure massive homogeneous white to light-tan limestone that is fairly soft and sometimes granular in appearance. It contains only a small percentage of very fine grained quartz sand, but locally it contains abundant fossil detritus
' and organic structures including casts, molds, and borings of mollusks and tests of Foraminifera and Bryozoa. The top of the formation, where it is not deeply buried by later deposits, has been locally silicified to irregular vitreous masses of translucent brown, red, and gray to black chert, some of which has been altered to porous white tripoli.
Stratigraphic relations. Elsewhere in Florida the Suwannee lime stone is known to be (Cooke, 1945, p. 88) unconformable upon older Oligocene (Mariarina limestone) or Eocene rocks (Vernon, 1951, p. 177) and is overlain unconformably by the Tampa or Hawthorn formation (Cooke, 1945, p. 88). The contacts of the Suwannee limestone were not observed in the area mapped for this report, although the contact with the Tampa limestone is probably present at localities 8, 65, and 70. At locality 65 a piece of rock dredged from a waterway contained two kinds of limestone in sharp contact. Part of the rock was com pact and contained molds of a nonmarine gastropod; the other part was porous and granular and contained Foraminifera. Other pieces of rock similar to the latter type contained Cassidulus gouldii, the Oligocene echinoid. Probably the Suwannee-Tampa contact was cut by dredging at this locality.
The Suwannee limestone is missing in parts of peninsular Florida, notably in the northeast corner of the area mapped and in the central part of the peninsula. The Tampa limestone and even the Hawthorn formation rest directly upon the Ocala limestone in some areas. Subsurface data show that the upper contact of the Suwannee lime stone is irregular (pi. 1 and figs. 2 and 3).
A limestone unit, which may be an equivalent of either the Byram formation or Marianna limestone of northern Florida, is present in a well drilled for the Davison Chemical Corp. in Polk County. Petro- graphic characteristics different from those usually shown by the Suwannee limestone were found in approximately the lower 40 feet of a limestone that is called Suwannee on the basis of lithology and the presence at the top of the unit of a fragment of Cassidulus gouldii. The anomalous lower 40 feet of limestone contained no fossils, but the quartz sand is coarser, the percentage of sand is higher, and the sorting poorer than in other limestone of the Suwannee analyzed from west-central Florida.
STRATIGRAPHY 11
I20-,
IIO-
100-
90-
eo-7O-
60-
50-
«0r 30-
X-
PMso, Pliocene and Miocene, uncflfferentiated, sand and clay
m Sea level-
60- 50-
40-
30-
20-
IO-
Sea tmel- 10- X-30.
PMsc,Pliocene and Miocene, A' undifferentiated, sand . I5'° 5 and clay ^ '
Qs,Quaternary sand
t' 0s,0ligocene, Suwannee
, Middle Miocene, Hawthorn formation Mt, Lower Miocene, Tampa limestone______
Contact Dashed where inferred
Top of first limestone.
G15 Number of core hole
Radionietric log, 5-foot averages, hundreds of counts per minute
location of the sectionsNumber of surface exposure Is snown °" P1 2
FIGURE 2. Sections through core holes hi northeastern and central Hillsborough County, Fla.
Fauna. Mollusks and Foraminifera are both abundant in the Suwannee limestone. An echinoid, Cassidulus gouldii (Bouve), is apparently diagnostic.
Fossils in the Suwannee limestone identified for this report are given in table 1.
Localities. A list of exposures of the Suwannee limestone examined by us is given at the end of the report (p. 72). Some of these localities are new to the literature.
PETROGBAPHIC DETAILS
Examination of the Suwannee limestone under the microscrope shows that it is composed mostly of calcareous mollusk and for- aminiferal detritus and a few scattered very fine quartz grains ce mented by microcrystalline dusky anhedral calcite or secondary quartz. Alteration textures include incipient fracture filling and minor replacement in and around fossils by fresh euhedral fine-grained calcite, and replacement of carbonate by crystalline and crypto- crystalline quartz. Silicification varies from tiny fossil molds filled with spherulitic chalcedony to massive chert replacement with only a few relicts of fossils. Some of the chert contains vugs lined with small quartz crystals. Pyrite is common in the darker chert. Much of the chert exposed to leaching has been partially altered to tripoli. Minor dolomitization shown by roughly rhomb-shaped areas of fine-grained optically continuous carbonate is also common in some specimens.
12 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
TABLE 1, Distribution of fossils in the Suwannee limestone, west-central Florida[All fossils except those marked-with asterisk (*) were identified by F. S. MacNeil; those marked with
asterisk were identified by E. R. Applin. See plate 2 for localities.]
;
Foraminifera:
: Rotalia mexicana Nuttall* . Asterigerina subacuta flo-
Coskinolina floridana Cole*....... . ...
Echinoidea: v Cassidulus gouldii
(Bouve) .... ....
Gastropoda: Cryoturrisl cf. C. hitts-
Fusiturricula sp. aff. F.
Orthaulax hernandoensis
Ceritheum pascoensis
brooksvillensis Mans field..... .... ...
sp. 'cf. C. suwanneensis
sp. afl. C. oaginatum Dall.... ._....
Turritella bowenae Mans field ... ............
sp. aff. T. bowenae
sp. aff. T. perduensis
Ampullina sp. ...........
Pclecypoda: Olycymerit suwanneensis
Eucrassatella sp. cf. E.
Chlamys sp. cf. C. brooks-
Phacoides sp. aff. P. chip-
Trigonocardium gadsde-
sp. cf. T. gadsdenense Mansfield ... ......
sp. aff. T. gadsdenense
Cardium cf. C. brooks-
hernandoense Mans field.. . ..... .
(Trachvcardium) n. so?.
. County and locality No.'
Hillsborough
40
X
46
X
X
X
X
04
X
X
X
O9
X
Pasco
63
X
X
X
65
X
X
X
X
67
X
X
X
X
y
X
X
X
70
y
X
Q109
X
X
G112
X
X
G113
X
Polk
72 G108
X
X
X
X
X
X
X
X
X X
See footnote at end of table.
STRATIGRAPHY 13
TABLE 1. Distribution of fossils in the Suwannee limestone, west-central Florida Uontmued .
:. ' " !-".' '
Pelecypoda Continued . Callocillista (PUaria) sp.
aff . C. imitabilis (Con rad)....:...... .......
Pitar sp. cf. P. heilprini
Pitaria sp ................Chione sp. cf. C. bain-
sp. cf. C. spada Ball ....sp. cf. .C. perduensis
Mansfield ______er|
Corbula sp ...............' j Myttaea sp. cf. M. lay-
'. Kuphus incrassatus (Gabb)............
Crustacea:
County and locality No.' ! j .
Hiilsborough
40
X
46
y
04
X
O9
X
Pasco,
63
X
65 67 70 Q109
X
X
G112 O113
Pplk '
72
X
G.108
X X
X :
X X
\ X
; x-.
" |i Q numbers are drill holes.
The Suwannee and most other limestones of Florida have high porosity, partly because of abundant fossil.casts and molds.
The Suwannee is a rather pure limestone. By calculation (see table below) samples chemically analyzed for this report contain from 64 to 99 percent calcium carbonate, and the average is 87 percent. Aside from minor amounts of quartz sand, silt, and clay, the percentage of other constituents is negligible.
i .Average of partial chemical analyses of 7 samples from the Suwannee limestone,
Pasco County, Fla. ,
[Laboratory Nos.: 115964-115968,115971, and 115972]
Percent
P205__-______________________ 0. 2Ca6_________________________ 48. 93Al203 -----------___-----_--.'. . 3
Fe 203 MgO.
Percent
0.28.42
The Suwannee limestone contains very few heavy minerals; several hundred grams of limestone yield only a few grains. In some samples muscovite is the predominant heavy mineral. In a composite sample from core-drill hole G108 nearly all of the heavy minerals were fine flakes of muscovite. ,
Quartz sand in the Suwannee limestone is very fine grained, ex tremely well sorted, rounded to subangular, and fairly .uniformly distributed. Petrographic data ob tained from samples of the Suwannee
50122,4 59 2
14 MIDDLE TERTIARY ROCKS IN PART OF WE.ST-CENTRAL FLORIDA
__.., , v Mt, Lower Miocene, ''Mhsc.Middle Miocene, Hawthorn Tampa limestone,
- - - -%^-Os, OliBOcene/ Suwannee limestone formation, sand and clay
EXPLANATION
Contact Dashed inhere inferred
G106 Number of core hole
Top of first limestone
Radiometric log, 5-foot averages, hundreds of counts per minute
Geologic logs of these holes are given In the text; location of the sections is shown on pi 2
2 Miles
FIGURE 3. Section through core holes in northwestern Polk and southeastern Pasco Counties, Fla.
are summarized graphically in figures 4-9. The data show that a typical sample of Suwannee limestone contains about 5 percent in soluble material; the sand fraction is about 2 percent of the sample and has a median diameter of 0.09 mm, a sorting coefficient of 1.14, and a fifth percentile value of 0.12 mm.
MIOCENE BOCKS
TAMPA MMESTONE
GENERAL FEATURES
Previous work. Alien (1846) was apparently the first to record ob servations of the rocks now known as Tampa limestone. In 1887 Heilprin (1887) assigned the rocks at Ballast Point on Hillsborough Bay to the lower Miocene, the present accepted age of the Tampa lime stone, but Johnson (1888, p. 235) was the first to use the name Tampa
STRATIGRAPHY 15
1.0 .9 .8 .7 .6 .5 .4 .3 .2 .15
GRAIN SIZE. IN MILLIMETERS
.1 .09 .08 .07 .06 .05
' . FIGURE 4. Typical cumulative curves of sand for Ocala, Suwannee, and Tampa limestones and Hawthorn
formation in west-central Florida.
to describe rocks exposed near Tampa, Fla. Dall and Harris (1892, p. 112) included in their "Tampa group" the "Chipola beds", the "Tampa beds", and the "Alum Bluff beds". Matson and Clapp (1909, p. 84-91) restricted the name Tampa to the limestone exposed near Tampa, but Mossom (1925, p. 77-82) included limestone exposed hi Hernando County in the Tampa, and later (1926, p. 182-1.84): he added the so-called Glendon limestone of Suwannee. and Hamilton Counties to the Tampa. In these reports Mossom:used the name "Chattahoochee" formation for limestone and calcareous clay hi northwest Florida which he considered contemporaneous with the Tampa limestone. Cooke and Mossom (1929, pi. 78-93) abandoned the name Chattahoochee and included these rocks with limestone of peninsular Florida in the Tampa formation. Later Cooke and Mans field (1936, p. 71) separated the Tampa and Suwannee limestones. Puri (1953b, p. 19-20, 38) divided the .Miocene in the Florida pan handle into 3 time-stratigraphic units, each separated by unconformi ties. He divided the lower Miocene Tampa stage into an updip clayey and silty Chattahoochee facies and a downdip calcareous St. Marks facies. He considered the St. Marks facies to be present hi the Tampa area (Puri, 1953b, p. 21),
16 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
MILLIMETERS
0.10 6.15 0.20 ! 0.25 0.30 0.35 0.40 0.45 0.50
Suwannee limestone 26 samples
Samples identifiechwitn certalnt iby fossils, or stratigraphic position
Tampa limestone 121 samples Samples which
to the formation on the of all available data
Noncalcareous samples of the Hawthorn formation;
MediansEntire formation
LimestoneHawthorn formation 116 samples
FIFTH PERCENTILE
Suwannee limestone 26 samples
Tampa limestone 121 samples
Hawthorn formation 117 samples Entire formation
Noncalcareous rock
SORTING COEFFICIENT
FIGURE 5. Frequency distribution of fifth percentile value and sorting coefficient in samples of Suwannee and Tampa limestones.and Hawthorn formation in west-central Florida. . <
MIL
LIM
ET
ER
S
. .-(
UP
-O
.IS
.0
.20
0.
25P
ER
CE
NT
25
3O -
^_
Tam
pa
limes
tone
-
-43
cal
care
ous
sam
ples
13
1 sa
mpl
es
over
50
perc
ent
inso
lubl
e
ME
DIA
N
DIA
ME
TER
Sam
ples
ide
ntifi
ed w
ith c
erta
inty
by
fos
sils
, or
by.
lith
olog
y an
d st
ratig
raph
lc p
ositi
on
;_
__
EX
PL
AN
AT
ION
D.
Sam
ples
whi
ch p
roba
bly
belo
ng
. to
th
e .fo
rmat
ion
on t
he
basi
s of
all
avai
labl
e d
ata
No
n-c
alca
reo
us
sam
ples
of
. .th
e H
awth
orn
-fo
rmat
ion
FIG
URE
6. F
requ
ency
dis
trib
utio
n of
med
ian
diam
eter
,' pe
rcen
t .sa
nd,
and
perc
ent
tota
l in
solu
ble
mat
eria
l in
sam
ples
of S
uwan
nee
and
Tam
palim
esto
nes
and
Haw
thor
n fo
rmat
ion
in w
est-
cent
ral F
lori
da..
- .
. '.'-
'.
1-3
I I o I
18 MIDDLE TERTIARY* ROCKS ; IN PART OF WEST-CENTRAL FLORIDA
Hawt
horn
form
atio
n.Lim
esto
ne o
f the
Tam
pa li
mes
tone
Clay
of t
he T
ampa
lim
esto
neSu
wann
ee li
mes
tone
Detri
tal(?
) lim
esto
ne (
Suwa
nnee
?)Oc
ala li
mes
tone
Hawt
horn
form
atio
nLim
esto
ne o
f the
Tam
pa li
mes
tone
Clay
of t
he T
ampa
lim
esto
neSu
wann
ee li
mes
tone
Detri
taK?
) lim
esto
ne (
Suwa
nnee
?)Oc
ala li
mes
tone
Hawt
horn
form
atio
nLim
esto
ne o
f the
Tam
pa li
mes
tone
Clay
of t
he T
ampa
lim
esto
neSu
wann
ee li
mes
tone
Detri
taU?
) lim
esto
ne (
Suwa
nnee
?)Oc
ala li
mes
tone
PER
CEN
T 10
20
30
40
50
6
^ ^H
i^m
^^m
-
Inso
lubl
e m
ater
ial
Sa
Cla
y ar
nd dsi
lt
0 70
S
I
0.0
0.10
0.20
MIL
LIM
ETE
RS
0.
30
0.40
0.
50
Hawt
horn
form
atio
nLim
esto
ne o
f the
Tam
pa li
mes
tone
Clay
of t
he T
ampa
lim
esto
neSu
wann
ee li
mes
tone
Detri
tal(?
) lim
esto
ne (
Suwa
nnee
?)Oc
ala li
mes
tone
Hawt
horn
form
atio
nLim
esto
ne o
f the
Tam
pa li
mes
tone
Clay
of t
he T
ampa
lim
esto
ne-
Suwa
nnee
lim
esto
neDe
trita
K?)
limes
tone
(Su
wann
ee?)
Ocala
lim
esto
ne
Hawt
horn
form
atio
n.Lim
esto
ne o
f the
Tam
pa li
mes
tone
Clay
of t
he T
ampa
lim
esto
neSu
wann
ee li
mes
tone
.Det
ritaK
?) li
mes
totre
(Su
wann
ee?)
Ocala
lim
esto
ne
*
- -
-
^m
M
10
1.20
1.
MM
MH
MM
MB
Med
ian
c
Fi
tth p
e
_
- -
-
amet
er
rcen
tile
30
1.40
1.
50
1.60
Sor
ting
ole
ffici
ent
FIG
URE
8. R
ange
s of p
etro
grap
hic
char
acte
rs o
f for
mat
ions
and
bed
s in
the
uppe
r par
t of D
avis
on C
hem
ical
Cor
p. c
hurn
-dri
lled
wel
l 3, S
EH
NW
J4se
c. 4
, T. 3
0 8.
, R
. 24
E.,
Polk
Cou
nty,
Fla
. .
!C
O
20 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
EXPLANATION
Hawthorn formation, 66 samples
xTampa limestone,
: 79 samples,' &* -- -
Suwannee limestone, 24, samples
bnArea of concentration
of Hawthorn forma tion analyses
Area of concentration of Tarppa limestone analyses
Soluble constituents Carbonate, phosphate
ESS],Area of concentra- :
tion of Suwannee 30, limestone anaiy- 70
ses
o so 10 40 Insoluble constituents, +230 mesh
Quartz sand ;PERCENTAGE BY WEIGHT
40 10 SO 0Insoluble constituents, ^-23fJ mesh
Clay and silt
FIGURE 9. Ternary diagram of soluble and insoluble constituents of limestone samples of the Suwannee and Tampa limestones and Hawthorn formation in west-central Florida.
Age and extent.' The Tampa limestone is of early Miocene age andin this report comprises all strata lying between the Suwannee lime stone of late Oligocene age and the Hawthorn formation, which is of middle Miocene age in this area.
The formation is near the surface from the Alafia River in west- central Hillsborough County northward and northeastward to central Pasco and north-central Polk Counties. Most of the exposures in this area are along the gulf coast from the vicinity of Clearwater in Pinellas County to Hudson in northwestern Pasco County, and along the shores of Tampa Bay and the Hillsborough River. Tampa limestone is also present in the bottom of two phosphate pits, one northeast of Lake land, the other west of Bartow (Mansfield, 1937, p. 22). We were unable to locate the exposure at Bartow and the location of the col lection may be hi error. The formation is also exposed in scattered areas in northwestern Florida. It has been found in wells throughout much of northwestern Florida, and is present in the subsurface as far east.as central Polk County in central Florida. The Tampa limestone
':. -. STRATIGRAPHY 21
appears to extend to extreme southern Florida where it was identified from a deep well in Monroe County (Cole,. 1941, p. 11). The formation once extended northward from the area mapped in this report but has been weathered and eroded from much of Sumter and Hernando Counties. Patches of the Tampa limestone remain, however (loc. 100, pi. 2), and in Hernando and northern Pasco Counties several feet of sandy clay have been identified (K. B. Ketner, oral communication, 1954) as Tampa. Thus the mapping of present studies has extended the Tampa northward from the area mapped by Cooke (1945).
In the area of this report the Tampa limestone averages about 75 feet thick, but the maximum exposure of limestone is only 9 feet.
General liihology. Limestone typical of the Tampa is white to light yellow, soft, moderately sandy and clayey, finely granular, and locally fossiliferous. Both marine and fresh-water limestones are present. Phosphate nodules occur in the Tampa limestone at a few localities (loc. 73 and drill holes G90 and G91, pi. 2). In places (Iocs. 4 and 26) calcareous fossil remains constitute as much as 90 percent of the rock. Many fossil molds give this type of rock a high porosity. Also present in the formation are lenses of limestone conglomerate, green and gray clayey sand, sandy clay, and clay-pebble conglomerate, all more or less calcareous, except where they have been deeply weathered. Chert is common, both as surficial crusts, and throughout the formation, as platy fragments. Fossils are ^beautifully silieified in;, some exposures (Iocs. 2 and 31). :
Stratigraphic relations. From evidence which will be presented later in the section on geologic history, we believe that erosiorial un conformities exist at the top as well as at the bottom of the Tampa limestone in most of west-central Florida. Few good exposures of the contacts are known in this area. Cooke (1945, p. 115) was not cer tain of the nature of the Tampa contacts, although he thought the Tampa limestone is probably unconformable upon the Suwannee at locality 8. No previous workers have conclusively stated the nature of the Tampa-Hawthorn contact hi the area mapped for this report, but an unconformity has been demonstrated between the lower and middle Miocene in northern Florida (Cushman and Ponton, 1932, p. 31; Mansfield, 1937, p. 84; Vernon, 1951, p. 153; and Puri, 1953b, p. 38).
Puri (1953b, p. 21) did not mention the existence of his Chatta- hoochee facies in the Tampa area, although lithologic zones are pres ent in the formation hi west-central Florida (loc. 26, fig. 10) that are similar to a section with which Puri (lQ53b, p. 20) illustrates his Chat- tahoocliee facies in northern Florida. 'We believe that both of Puri's facies may be present in west-central Florida. The intertonguing of relatively pure limestone and calcareous sandy clay is common hi this area, but hi most of the region such relationships can be studied only by means of well logs.
to
to
Hill
sbor
ough
Riv
er
Wat
er l
evel
O
Pot
hole
EX
PLA
NA
TIO
N
Ste
ep e
dge
of o
utcr
opC
lay
seam
s
10
0
Con
tact
bet
wee
n be
ds
Dot
ted
whe
re c
once
aled
Foss
ils
Map
ped
by t
ape
and
com
pass
Woo
d pi
lings
1020
30 F
eet
FIQ
UEE
10.
Ske
tch
map
and
sec
tion
of T
ampa
lim
esto
ne a
t loc
ality
26,
Hill
sbor
ough
Riv
er d
am, H
illsb
orou
gh C
ount
y, F
la.
Exp
lana
tion
of s
ymbo
ls a
nd p
etro
grap
hic
prop
ertie
s of
sam
ples
are
giv
en o
n th
e fa
cing
pag
e.
O M
Iscf
lim
esto
ne,
light-
tan t
o w
hite
, sl
ight
ly s
andy
, sl
ight
ly c
laye
y;co
ntai
ns a
bundan
t m
olds
and
cas
ts o
f m
ollu
sks.
'.
Ics l
imes
tone
, w
hite
to
li
ght-
tan,
sl
ight
ly
sand
y,
clay
ey,
fair
lyha
rd,
frag
men
tal,
spa
rsel
y fo
ssil
ifer
ous;
con
tain
s li
ght-
gree
n to
whi
te c
lay
and l
imes
tone
gra
nule
s an
d pe
bble
s, a
nd t
hin
sea
ms
of t
an s
econ
dary
car
bona
te.
lose
lim
esto
ne,
light-
tan
to
ligh
t-gr
ay,
slig
htly
sa
ndy,
cl
ayey
,so
ft,
loca
lly
frag
men
tal;
co
ntai
ns th
in l
ense
s an
d p
arti
ng
s of
very
san
dy l
ight
-gre
en-g
ray
clay
. .
sec
sa'n
d,
whi
te,
quar
tz,
fine
-gra
ined
, ve
ry c
laye
y, v
ery
calc
areo
us,
mod
erat
ely
indura
ted;
cont
ains
sm
all
irre
gula
rly
dis
trib
ute
d
patc
hes
or f
ragm
ents
of
ligh
t-gr
ay-g
reen
cla
yey
sand
.Is
c l
imes
tone
, w
hite
to
ligh
t-ta
n, v
ery
sand
y, c
laye
y, f
airl
y so
ft;
cont
ains
spa
rse
irre
gula
r pa
tche
s of
cla
yey
slig
htly
ca
lcar
eous
gr
een-
gray
san
d an
d ab
un
dan
t pe
bble
s an
d g
ranu
les
of s
ligh
tly
. sa
ndy
hard
, whi
te l
imes
tone
.sc
^-sa
nd,
gray
-gre
en t
o w
hite
, qu
artz
, fi
ne-g
rain
ed,
very
cla
yey,
sl
ight
ly
calc
areo
us,
poor
ly
indura
ted;
cont
ains
su
rfic
iall
y in
d
ura
ted
san
dy c
oncr
etio
nlik
e st
ruct
ures
.
Sum
mar
y of
pet
rogr
aphi
c pr
oper
ties
of
sam
ples
(lo
cati
ons
show
n on
figu
re 1
0) g
roup
ed b
y li
thol
ogy
and
stra
tigr
aphi
c po
siti
on
Cla
y an
d si
lt___
___
___
___
do
_ _-
Rat
io o
f sa
nd t
o cl
ay _
___
____
__
_
Med
ian
diam
eter
of
sand
..m
illi
met
er-
S
orti
ng c
oeff
icie
nt o
f sa
nd _
_
____
__
_F
ifth
per
cent
ile.
__
____
.m
illi
met
er. .
s
26A
1 60 29 2. 1 89 11
0. 1
5 1.
20
0.2
2
c ' 26
B1 58 35 1.
7-
93 7-0.
13
1. 22
0.22
26A
2 27 11
-
2.5 38 62
0. 1
5 1.
23
0. 2
2
Isc 26B
3 22-
17 1.'3 39 61
0. 1
3 1.
22
0. 2
3
26C
1 .
23 16 1.4 39 61
0. 1
4 1.
20
0. 2
3
26B
2 33 33 1:'0
-66 34
0. 1
2 1.
34
0.2
5
sec
26C
3 27 24 1.
1 51 4Q0.
14
1. 2
30.
24
26C
4 AQ 23
2. 1 72 28
0. 1
4 1.
21
0. 2
4
Ic
26A
3 421
0.2 25 75
0. 1
0 1.
19
0. 1
6
sc
26B
4 19 18
0.7 30 70
0. 1
2 1.
23
0.21
26A
4 10
110.
9 21 790.
13
1. 2
10.
21
les
26B
5 821
0. 4 29 71
0. 1
2 1.
22
0. 1
9
26C
5
8 100.8 18 82
0. 1
2 1.
23
0.2
0
Q bO CO
24
Fauna. The Tampa limestone is erratically fossiliferous. In places it is practically a coquina of mollusks whereas other exposures are completely devoid of megafossils. The fauna of the Tampa in west- central Florida is characterized by ^abundant marine mollusks, and several species of land and fresh-water snails are present. Charophyte (fresh-water plant) seeds and insect borings are locally abundant. Exposed at Ballast Point (loc. 2) near Tampa is the "silex bed" or Orthaulax pugnax (Heilprin) zone from which Heilprin (1887), Ball (1890-1903, 1915), and Dall and Harris (1892) described a variety of beautifully preserved silicified mollusks. Common at some localities, notably Sixmile Greek (loc. 1), is Celliforma nuda (Dall)v which is thought (Brown, 1934, 1935) to be the silicified larval chamber of a mining bee. Foraminiferia are present, particularly in the lower part of the formation (Puri, i953b, p: 17). An association of the three Foraminifera Sorites, Camerina, and Peneroplis was noted by F. S. MacNeil in samples collected by us from several localities at which the Tampa is found. Archias is one of the most abundant forms identified in well logs of the Tampa. Only one echinoid, Lovenia clarki (Lam bert), has been found in the Tampa limestone.
Terrestrial vertebrate fossils, some of which have lower Miocene affinities and are associated with depressions or sinkholes in the Tampa, Suwannee, and Ocala limestones in northern Florida, are described by Colbert (1932, p. 55-58), SeUards (1916, p. 82-90), Simpson: (1930, p. 160; 1932, p. 7-41), White:(1942), Wetmore (1943), and others, but none of these remains have been found in the Tampa formation proper.
Silicified corals of the genus Siderastraea from several localities were identified by J. W. Wells of, the Geological Survey. All but one of these were identified as S. hillsboroensis Vaughan; the remaining one was S. silicensis Vaughan. Siderastraea hillsboroensis seems to be associated with the Tampa-Hawthorn contact, or the lower part of the Hawthorn where the Tampa is absent.
Fossils from the-Tampa limestone identified for this report are given in table 2. i ; i ,
Localities. A list of exposures of the Tampa limestone examined by us is given at the^end of the report (p. 75). Many of these localities are new to the literature. Localities in operating phosphate mines are usually impossible to;relocate, as conditions there change daily.
1 PETROGRAPHIC DETAILS
The exposure at locality 26 shows some of the features of the Tampa limestone (fig. 10). pathology varies from a relatively pure limestone at the top of the section to a slightly calcareous clayey sand at the bottom. The beds are only a few inches to a foot or so thick and
STRATIGRAPHY ' ) -^ 25
pirich! out or merge laterally into different lithologiesi Note (fig. 10), however, the lateral continuity of petrographic. data of samples from the same beds. Contacts between most beds are gradational over an inch: or two and are gently undulating to irregular. Clay fragments are abundant in places; some are cemented by a network of veihlets of 'calcium carbonate. Pockets of clayey ! sand surrounded by;calcareous clayey sand are common. ; i j ;
Most clayey beds in the Tampa limestone are small lenses, but .several wells in Polk County, including two drilled in! 1952 at the Davisori Chemical Corp. in western Polk County, were drilled through about 50 feet of rather uniform greenish-gray dolomitic sandy clay (fig. 7). This unit is tentatively placed at theibas&of the' Tampa; in the Davison wells it rests in sharp contact upon pure, white lime stone containing fragments of the Oligocene echijnoid, Cassidulus gouldii (Bouve"). The wells hi which the unit was noted roughly delimit an ;area with corners near Mulberry, Lakeland, Winter Haven, and Fort Meade. . : : i ;
A limestone breccia, which appears tio be characteristic of the Tampa limestone in some areas, is developed in several exposures near Tampa (Iocs. 1, 19, 20, and 25), and is present, though poorly developed, at many other exposures. Angular t,o rojunded fragments of relatively pure, white fine-grained limestone from a few millimeters to 10 centimeters in diameter are cemented in a' matrix;of light-gray to light-tan carbonate containing abundant fine-tgrained; quartz sand. Cooke (1943, p. 87) and Stevenson and Veatch (1915, .p. 88) noted
;a similar structure in Tampa limestone of; southern Georgia.At least two methods by which this structure formed may be con
sidered. Much of the Tampa limestone, which is relatively soft when wet, becomes quite hard when dried by exposure to: the air. Smooth vertical grooves made by the teeth of a power shovbl when the lime stone was wet and soft are plainly preserved in one exposure (loc. 20) of dry, hard limestone. Alternate wetting and drying of the lime stone due to fluctuations of the water table could produce a network of cracks into which sand grains could work down from the surficial .cover. A prolonged rise of the water, table npight then cause the cracks to be sealed by precipitation of secondary carbonate. Several observations support this theory. Firstr most of the fragments are angular; only a few show any rounding., Soijne of the fragments "fit together" as if they have been separated only a few millimeters. There is a tendency in some exposures for the fragments to decrease in size upward in the outcrop, and for the "fractures" to become tighter downward. i ;
2Q MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
a 8
CQ «*H
Q 5
County and locality No.i
Pinellas
M
(?.
81PL,
Hillsborough
CO
sso
§s Ss . osoJ2
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S
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S
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8
.S
S
.«8.
3
g
S
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«»<
V *
X
X
X
X
Foraminifera: da.mp.rinn sn
X
X
X
X
X
X
X
X
X
X
XX
X
,5
!1
X
t,
cI.W
«c.2 'C
S
. -
X
Gastropoda nonmarine:
tCepolis direpta (Dall) ____
Pleurndonte sn _
X
X
Bulimulus heilprinianus DalL
? sn ______
X
X
X
X
X
X
Cerion anodonta (Dall)..l ....
fff.lisama sn
Gastropoda marine:
Tf.rehra sn
X
X
Conus sp. cf. C. ittiolus DalL.
'nlanicens Heilnrin
X X
X
X
X
1
c\v
17*s c
'£
S
X X
X
Knefastia sp. aff. K. brooks- villensis Mansfield . _
Olivella sp. cf. 0. posti DalL.
y4 nrilla shp.nardi Dull
X
1, c2
1$
X
X
Fasciolaria petrosa Dall _ __ Latirus sp. cf. L. floridanus
"firp.ilnrm
X
5o-
X
CV
11
X
1
X
Melongena turricula Dall .....
Solenosteriat quinquespina
rn»in
X
X
Murex sp. cf. M. trophoni- formis Heilprin.... ...... Cypraea sp. _
Mor
um d
omin
gens
e (S
ower
- by).
.............. ..
.....
Ort
hdul
ax p
ugna
z (H
eDpr
in)
Dal
l. .........
...........
Cer
itheu
m s
p. a
ff.
C.
geor
gi-
sp_.
..
....
....
..P
otam
ides
(P
yraz
isin
us)
hills
-
(Pyr
azis
inus
) ca
mpa
nula
-
? sp
................. ..
Turr
itella
tam
pae
Hei
lprl
n ..
.
cf.
T.
atac
ta D
all.
.. _
__
_
Cal
yptr
aea
sp.
aft.
C.
cren
ata
Am
auro
psis
ap.
aff
. A
. bu
rn-
Pele
cypo
da:
Bar
batia
sp.
cf.
B.
mar
ylan
- di
ca C
onra
d _____ ..
...
sp.
cf. A
. hy
pom
ella
Dal
l ...
SP
- . .-.. ... -
X
X X
X
X
X X X X X X
X
X X
X
X
X
o
a i
See
footn
ote
at
end
of t
able
.
bO
28 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
83 JO ' £a o O
^ s
H
6 K £
a%
Io O
Pinellas
2 (S
8S PM
Hillsborough
S *CD
S
Os130>OS- oB
g
S>oCO
IOsosco O
8s *eo
3
CN W
CO
gsgs8
rl
to
*
X
X
X
Pelecypoda Continued
Chlamys crocus (Cooke). . ....
burnetii Tucker.. __ cr, off r> /.M*ln7/>*>»f» Doll
|X
X )
X
X
n. sp..._. .................. sp....... .... . ... Anomia sp .
< X)
d
& Io ,° § aS fe S ft,
<
X
><
X
X
X
Cardita sp ...
Venericardia serricosta (Heil- prln). ...... ..... ...
sp. cf. V. serricosta (Hell prin) . ..............
X
X
X
sp. _....--.-. - . Cyrena sp. cf. C. pompholyx Dall. ... _ ...........
X
<
>
X
X
floridana Dall _ .. __ .....Chama tampaensis Dall...... Phacoides sp. cf. P. wacissa-
nus Dall--.---- __ .
X
X
X
hillsboroensis (Heilprln) .... sp. cf. P. hillsboroensis (Hellprin)-. _ ... -
X
X
X
Divaricella n. sp.?. ___ .-
Trigonocardia alicula Dall ....
x
<
X
%
X
Sf ................ ... ...... Cardium delphicum Dall ..... sp. cf. C. andotensis Mans-
flolH
X
X
X
sp. cf. C. pineUasense Mansfield ___ _ ...... sp. aff. C. taphrium Dall _
X
X
X
X
LidSS&
Cal
loca
rdia
sp
... .
....
....
...
shep
ardi
Dal
l... ..
....
....
.S
p... ...--..._
.....-
.._..
Pita
r sp
....
....
....
....
....
..
Chi
one
nuci
form
is (
Hei
lpri
n).
rhod
ia D
all _
__
__
__
__
Ano
mal
ocar
dia
peni
ta
(Con
-
Veh
us h
alid
ona
Dal
l. .......
sp. .
............
...........
sp. ..
...................
Inse
cta:
C
ellif
orm
a nu
da (
Bro
wn)
.....
Cha
roph
yta:
C
haro
phyt
e sp
. (o
ogon
ia) .
__
X X X
X XX
X
X
X X
X X
X
X
X X X
X
i Q n
umbe
rs a
re d
rill
bol
es.
G bo
30 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
It is also possible that the fragmental structure was formed by breaking up of limestone along a beach in early Miocene time, the resulting fragments being immediately 'buried by beach sands and recemented by carbonate without much reworking. The shallow marine and fresh-water environment of the Tampa, the presence of a few fragments that are well rounded, a possibility that most of the occurrences of this feature are near the same stratigraphic level, and the fact that in some places the fragmentation does not extend to the upper surface of the limestone, support the latter theory.
Chert similar to that developed locally on the Suwannee limestone is found on or near the top of the Tampa, but well logs indicate (Heath and Smith, 1954, p. 13) that thin seams of chert are also present throughout the formation. Some of this chert within limestone may be syngenetic; some or all of it may have developed during periods of local intraformational weathering.
A variety of textures may be seen in thin sections of the Tampa limestone. The rock is dominantly microcrystalline, but may be largely organic. Locally it shows much alteration. ;
The chief constituent, calcite, is microcrystalline, uniformly grained, and usually cloudy in appearance due to inclusion of minute clay particles. Very fine grained subrounded to angular clear quartz sand is rather irregularly distributed through the rock. Detrital particles of limestone and clay as much as 10 mm in diameter are present locally. The smaller grains are commonly casts of Foraminifera tests. In Tampa limestone that contains clay and limestone fragments the quartz sand is invariably more abundant and usually coarser in the interstitial carbonate.
Crystalloblastic textures are common in the Tampa limestone. A thin section of a sample from locality 11 showed a microcrystalline limestone cut by veinlets as much as 1 mm across and containing, in order of deposition, fresh calcite, thin septa of cellophane, and micro- crystalline and spherulitic quartz. Most of the veinlets seen in thin section seem to be replacements, but a few were apparently open fractures, as they alternately pinch and swell like some metalliferous veins. Some veinlets appear to have been localized along concentra tions of microfossils.
Locally, as at localities 2 and 27, the Tampa limestone is completely silicified. At locality 2 (Ballast Point) the rock is a massive chert that contains vugs with chalcedony, quartz crystals, and opal, some of which is dark blue and orange. Replacements of fossils by quartz are common. At locality 27 the rock is a silicified sandstone in which the quartz grains are nearly in contact and the cement is microcrystal- line and spherulitic quartz. Silicification such as this, in which the quartz sand may be seen, is rare, however. Chert is most common in
STEATIGBAPHY 31
the purer beds of limestone of the formation, particularly those which may have been deposited in fresh water.
Limestone from the Tampa at locality 73 deserves special mention, because it differs texturally from the majority of other Tampa samples studied. There are three types of carbonate present in this rock: (1) fresh coarse-grained crystalline carbonate that occurs mostly as fossil replacements and small veinlets, (2) gray microcrystalline dusky carbonate in the form of detrital rock fragments as much as 10 mm in diameter, some of which are partially replaced and cemented by (3), a brown iron-stained microcrystalline carbonater The quartz sand, which is unusually coarse grained for the Tampa limestone, is present with fossil fragments in the brown carbonate between the rock fragments. These rock fragments have only a few very fine quartz sand grains. This occurrence of the Tampa limestone must be very near the top of the formation; elsewhere in pits in the same area, and at the same level, pieces of limestone, probably Hawthorn, were found. Although the fossils (table 2) in the rock described above indicate an early Miocene age, the cementing ma terial, including the coarser quartz sand, may be middle Miocene in age.
In contrast with the Suwannee the Tampa limestone as a whole is relatively impure, and contains considerable clay and sand. There is, however, much pure limestone in the formation. Chemical analyses of 16 samples of relatively fresh limestone from the Tampa showed a range in calcium carbonate content from 73 to 96 percent. The average composition of these samples is given below.
Average of partial chemical analyses of 16 samples of limestone from the Tampa limestone, Hillsborough, Polk, and Pinellas Counties, Fla. .
[Laboratory Nos.: 115933-115937, 115939, 115940, 115942, 115944-115946, 115948, 115960, 115973, 115988, 115989]
. Percent
P205,-.--------------------- 0. 3CaO---_____-_-----__-_______ 47. 49A1203-- ------------------- 1. 2
Fe203 - MgO-
Percent0. 41.82
The Tampa limestone generally contains less than 5 percent MgO. The few known exceptions to this are: (1) a sample from an outcrop (loc. 91) that is presently exposed to sea water, and which contained 15.25 percent MgO; (2) samples from the Davison well where the principal mineral in the lower part of the Tampa limestone is dolomite; (3) samples believed to be from this same zone in the lower part of the Tampa in a well at the Peace Valley mine (loc. 82) of the International Minerals and Chemical Corp.; 2 and (4) one of 18 drill-hole samples
2 Unpublished log in the files of the Florida Geological Survey.
32 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
from southwestern Pasco County, reported by Hopkins (1942, p. 72-73), and which contained 11.02 percent MgO.
Phosphate nodules were found hi the Tampa limestone, particularly in northern and central Polk County. At two localities (1 and 26) of the Tampa limestone secondary phosphate minerals, wavellite or pseudowavellite, were detected by X-ray in samples that were mega- scopically nonphosphatic and that were overlain by relatively fresh limestone.
Nineteen samples of clay fractions of the Tampa limestone, both fresh and weathered, were analyzed by X-ray spectrometry. In 11 of these samples illite was detected, and in 10 of these it was the only clay mineral present. MontmoriUonite was found in 8 of the samples, attapulgite (hydrated silicate of aluminum and magnesium) in 4, kaolinite hi 2, and chlorite-vermiculite in 1. Thus, illite appears to be the predominant clay mineral in the Tampa limestone, but clay minerals of the other groups are also present.
The presence of attapulgite hi the Tampa limestone is previously unreported, although Berman (written communication, 1953) found it hi the topmost part of the Hawthorn formation and in the Bone Valley formation. Attapulgite was found in Tampa limestone from localities 1 and 20, at the probable top of the formation in core hole G3, and in the Davison well. Fresh-water plants or gastropods have been recorded from these two localities and from core hole G3 (table 2; and Mansfield, 1937, p. 20). Attapulgus clays have been reported (Kerr, 1937) from the Hawthorn formation in northern Florida and southern Georgia in beds associated with terrestrial vertebrate re mains. X-ray analyses by R. G. Petersen (oral communication, 1955), and studies by Berman (written communication, 1953), show that attapulgite commonly is found with the dolomite hi the upper most part of the Hawthorn formation, which underlies the phosphate deposits in the land-pebble phosphate district.
Heavy minerals are far more abundant in the Tampa than in the Suwannee limestone, but the amount is still very small. About 100 grains +100 mesh are usually present in 100 g of limestone. Pale pink garnet is by far the most abundant heavy mineral, often exceed ing 40 percent of the heavy fraction. Staurolite, tourmaline, and opaque minerals, which include considerable black tourmaline and a small amount of collophane, are present in about equal amounts, and each comprises 10-15 percent of the heavy fraction. Epidote, kyanite, rutile, sillimanite, sphene, topaz, zircon, and zoisite are also present in amounts of 1-10 percent.
Petrographic data obtained from samples of Tampa limestone are summarized graphically in figures 4-9. Quartz sand from the Tampa has a narrow range of median diameters; 65 percent of the samples
STRATIGRAPHY 33
fall in the range between 0.12 and 0.14 mm; and the median of all samples is 0.13 mm. Sixty-six percent of the Tampa samples have a sorting coefficient between 1.17 and 1.27, and the median of all samples is 1.22. Sixty-four percent of the Tampa samples have a fifth percen- tile value between 0.19 and 0.25 mm, and the median for all samples is 0.22 mm.
Previous work. Dall and Harris (1892, p. 108) named the Hawthorn formation from exposures in Alachua County, Fla. Matson and Clapp (1909, p. 69-74) included in the Hawthorn part of the limestone now called Suwannee, and designated beds of phosphatic limestone, sand, and clay in central Florida as the Hawthorn formation. The name Hawthorn was abandoned by Vaughan and Cooke (1914, p. 251) who showed that the Hawthorn is nearly equivalent to the Alum Bluff formation as defined by Matson and Clapp (1909, p. 91). Gardner (1926, p. 2) raised the Alum Bluff formation to the rank of a group, divided it (ascending) into the Chipola formation, Oak Grove sand, and Shoal River formation, and expressed the opinion that the abandoned Hawthorn formation was equivalent to the Chipola forma tion of the Alum Bluff group. Cooke and Mossom (1929, p. 115, 116, 133-135) revived the name Hawthorn for beds in Florida orig inally defined by Matson and Clapp (1909, p. 91), and also concluded that the Hawthorn is equivalent to the Chipola formation. They extended the Hawthorn formation into the land-pebble phosphate district, but excluded the Oligocene beds that Matson and Clapp (1909, p. 69-74) placed in the Hawthorn formation and called Tampa lime stone. Cooke (1945, p. 137) dropped the term Oak Grove formation, classifying the Oak Grove as a member of the 1 Shoal River, and also extended the Shoal River formation upward to include basal faunal zones (Yoldia and Area) previously included in the Choctawhatchee formation. In 1953, however, Puri (1953b, p. 21-22) proposed the Alum Bluff and Choctawhatchee as stages, with Oak Grove, Shoal River, Chipola, and Hawthorn as facies of the Alum Bluff stage. He excluded from the Alum Bluff stage the Yoldia, and Area, faunizones.
Age and extent. Although the exact age of the Hawthorn formation has not been clearly stated in the literature, in the opinion of F. S. MacNeil (oral communication, 1955) it is middle Miocene. Vernon (1951, p. 188) believes the deposits he mapped as Hawthorn forma tion in Citrus County are of middle Miocene age. In the area of this report the Hawthorn formation includes dolomitic limestone, calcitic dolomite, clay, and sand of middle Miocene age above the Tampa limestone and below deposits of late Miocene age. There are numerous areas in northern peninsular Florida where unfossiliferous clayey
34 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
phosphatic sands have been placed in the formation on the basis of their none too distinctive lithology.
The Hawthorn is the most extensive upper Tertiary formation in Florida, and is missing only from parts of the Ocala uplift in north western peninsular Florida. The formation also extends across southeastern Georgia into southern South Carolina. In Florida it lies near the surface in a long curving, discontinuous belt that begins in the panhandle of Florida at about long. 85° W., extends eastward along the Georgia border, and thence south-southeastward into cen tral peninsular Florida. In the area of this report the formation is exposed in northeastern Pasco County, in the phosphate district of Hillsborough, Polk, Hardee, and Manatee Counties, and in western Sarasota County. In southern Hillsborough and Polk Counties the formation is about 100 feet thick, but it thickens southward to about 300 feet near Sarasota. Northward from the land-pebble phosphate district it thins rapidly, is almost completely eroded from the valleys of the Withlacoochee and Hillsborough Rivers, and then reappears in the highlands of northeastern Pasco County. There it is not over 100 feet thick, and may average only about 25 feet thick.
General lithology. Four lithologic divisions (fig. 11) of the Hawthorn formation were recognized during this work. Their relations are obscured by weathering and scarcity of good outcrops and fossils. The four units are: (1) A lower limestone unit yellow to white soft irregularly sandy and clayey massive dolomitic limestone and calcitic
Contact between divisions of formation
Vertical scale greatly exaggerated
FIGURE 11. Diagram showing the relation between the four divisions of the Hawthorn formation in the area between the Withlacoochee and Manatee Eivers in west-central Florida.
STRATIGRAPHY 35
dolomite; contains a few clay lenses, sparse phosphate nodules, and a fauna like that of the Oak Grove sand member of the Shoal Kiver formation. (2) An upper limestone unit gray to white slightly sandy arid clayey soft massive dolomitic limestone and calcitic dolomite; contains sparse phosphate nodules of sand size and a fauna similar to the part of the Shoal River formation above the Oak Grove sand member. (3) A phosphorite unit locally calcareous gray-green to tan sand and clay; contains abundant phosphate nodules, but gener ally is unfossiliferous. (4) A sand unit gray to red and orange- brown often mottled sand and clay; contains traces of phosphate nodules, locally abundant secondary phosphates, and rare lower middle Miocene fossils. .
These units owe their distinctive lithology, in part at least, to weathering. The upper limestone unit is south of the mapped area (pi. 1) in Hardee and Sarasota Counties; the phosphorite unit and the sand unit are mapped together and shown only where they do not overlie the lower limestone unit.
Stratigraphic relations. In the panhandle of Florida the Hawthorn formation is replaced by its equivalents in the Alum Bluff group: the Chipola formation and Shoal River formation, which includes the Oak Grove sand member. The Hawthorn formation of the area of this report is equivalent to only the Shoal River formation, but in other areas equivalents of the Chipola are included in the Hawthorn. According to MacNeil (oral communication, 1955) the fauna of the lower limestone unit of the Hawthorn formation, which underlies the phosphate deposits of Polk and Hillsborough Counties, is most like the fauna of the Oak Grove, but to the south of the phosphate district the limestone exposed (the upper limestone unit) is younger and faunally like, but not typical of, the part of the Shoal River formation above the Oak Grove sand member.
The Hawthorn formation is unconformable upon the Tampa lime stone. It overlaps the Tampa and rests in places upon the Suwannee and Ocala limestones although in some areas sand and clay of the Tampa limestone intervene between the Hawthorn and pre-Miocene formations. The Hawthorn is overlain unconformably by the upper Miocene, Pliocene, and Quaternary deposits. Of these beds the Bone Valley formation is the most important in the land-pebble phosphate district.
The phosphorite unit of the Hawthorn lies upon (fig. 11), and is a result of weathering of, the lower and upper limestone units, but the relation between the lower limestone unit and the sand unit is not clear. The sand unit may be a weathered equivalent of part or all of the lower limestone unit or it may be an originally clayey and sandy facies of the formation. In addition, no known exposures show the
36 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
relation between the sand unit and the phosphorite unit, but it is inferred by the increase in clay and phosphate content that the sand unit passes southward into the phosphorite unit.
Fauna. Locally limestone of the Hawthorn formation is quite fossiliferous, but the fossils are usually poorly preserved as a result of leaching and dolomitization. Mollusks, particularly large oysters and pectens, are conspicuous in the fauna of the formation. The oyster, Ostrea normalis Dall, is apparently diagnostic, but similar oysters occur in the Tampa limestone. The large pectens, Chlamys acanikos Gardner and Chlamys sayanus Dall are characteristic. Other common molluscan genera include Area, Chione, Cardium, and Venus. Foraminifera are rare in exposures of the formation. Gush- man (1920) reported a few species from the Alum Bluff group. A few silicified fossils are found in weathered portions of the formation. As discussed under Tampa fauna, Siderastraea corals are the most common of these, but silicified oysters are also locally abundant.
Sharks teeth are particularly common in the Hawthorn and other vertebrate fossils have been found in it in northern Florida. A list of Hawthorn fossils identified for this report is given in table 3.
Localities. A list of exposures of the Hawthorn formation examined by us is given at the end of the report (p. 82). Many of these localities are new to the literature. Localities in operating phosphate mines are usually impossible to relocate, as conditions there change daily.
PETROGRAPHIC DETAILS
Limestone of the Hawthorn is microcrystalline in texture; in thin section it is a highly birefringent mass composed of uniform anhedral calcite crystals and evenly dispersed dolomite rhombs. Irregularly distributed through this matrix are variable amounts of phosphate nodules and quartz grains. Most of the dolomite crystals have round nuclei and appear to have grown at the expense of the calcite. In some specimens there are irregular areas of more sandy slightly coarser grained carbonate, which probably fill cavities left by removal of fossil remains.
Phosphate nodules are more widely distributed than in the Tampa limestone, but seldom constitute more than 15 percent of the rock. Phosphate is most abundant in the sandy clay beds, and much of it, together with quartz sand, occupies small irregular pockets in the rock. The phosphate nodules may be almost any color and size, but tan, gray, and brown sand- to pebble-size nodules are most common. They are typically oval in cross section, but some are flat. The ex terior of the nodules has a soft greasy lustre. They have been identi fied (Altschuler and Cisney, 1952) as carbonate fluorapatite. Another type of nodule, common in places, ranges from pebble to boulder size,
TAB
LE 3
. D
istr
ibut
ion
of fo
ssil
s in
the
Haw
thor
n fo
rmat
ion,
wes
t-ce
ntra
l F
lori
da
[All
foss
ils w
ere
iden
tifie
d by
F. S
. Mac
NeQ
. Se
e pla
te 2
for l
ocal
ities
]
Gas
trop
oda:
Pel
ecyp
oda:
A
nada
ra d
odon
a B
all. _
__
__
__
__
__
__
_ _
_______________
Cal
loar
ca s
p. c
f. C
. phd
lacr
a D
all _
_____________________
Pte
riasp
... _
____________________________ . .
....
...
sp.
cf.
C.
burn
sii
Dal
l _____________________________
nich
olsi
Gar
dner
__
__
_ _
__________________
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38 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
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STRATIGBAPHY 39
and is apt to be pitted, porous, and irregular in shape. These are apparently pieces of phosphatized limestone, as many have only a thin coating of cellophane over an interior of partially phosphatized limestone which may contain quartz sand, fossils, and smaller phos phate nodules. This type of nodule occurs mostly at the top of, or just above, the limestone in the phosphate mines, and in many places may be a basal conglomerate of the overlying Bone Valley formation.
The typical cellophane nodule as seen under the microscope is iso- tropic, oval in outline, 1-5 mm in diameter, and is a rather homogeneous yellow brown. The phosphatized limestone type of nodule is usually weakly anisotropic. None of the phosphate nodules seen in thin section exhibited any concentric structure. The carbonate surround ing the nodules is apparently undisturbed, except in rare cases where a thin zone of later carbonate peripherally replaces the nodules.
A summary of chemical analyses of limestone of the Hawthorn formation is given below.
Average of partial chemical analyses of 26 samples of limestone of the Hawthorn formation, Hillsborough, Polk, Manatee, and Sarasota Counties, Fla.
[Laboratory Nos.: 115930-115932,115951-115956,115974-115980,115982-115986,115990-115994]
Percent Percent
P2 05 ----------------~------- 2.0CaO----._-._._...._-.--.-.,- 30. 35Al203 .--_-__-_______-._.... .9
Fe203 ----______ - ______ 0. 49 MgO...-......._.__.__.... 15. 28
From calculation the average ratio of CaCO3 to MgCO3 in these sam ples is about 1.7 to 1. Some of the magnesium is in clay minerals. Montmorillonite is present (Berman, written communication, 1953), in the overlying Bone Valley formation. Berman found that attapulgite partly supplants montmorillonite in the top of what he called the Hawthorn formation. He found as much as 35 percent attapulgite in the samples of limestone of the Hawthorn, and as much as 73 percent in the base of what he called the Bone Valley formation. Several samples of the Hawthorn formation from phosphate mines and one sample of Hawthorn formation from 160 to 170 feet in the Davison well were X-rayed by R. G. Petersen. The well sample contained montmorillonite and illite; all the mine samples contained attapulgite associated with dolomite.
Every sample of limestone of the Hawthorn chemically analyzed contained at least 9 percent MgO, but all the samples came from within a few feet of the upper surface of the limestone, so that these analyses are not representative of the formation. Hopkins (1942) in a study of dolomitic limestones of Florida found that limestone of the Hawthorn in Manatee and Sarasota Counties, where it is mined for dolomite, has an erratic MgO content. His samples were taken from drill holes
40 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
that did not penetrate more than 30 or 40 feet into the formation. The MgO content ranged from 1 to 20 percent.
The PzOs content of the limestone is low in all samples and does not exceed 9 percent. The uranium content of raw samples of limestone of the Hawthorn was found to be negligible.
Alteration of limestone of the Hawthorn consists of dolomitization, rare incipient replacement of carbonate by microcrystalline spherulitic quartz, and formation of residues of phosphatic clayey sand by weathering.
The following section illustrates in detail the lithology of the lower limestone unit of the Hawthorn. This exposure is near the base- of the formation,
Locality 10, W% sec. 21, T. SO S., R. 20 E., below bridge in ravine about 1 mile southeast of Riverview, Hillsborough County, Fla.
[Numbers arc sample numbers]Approximate
^ , thickness Quaternary: (/< ,- )A7. Sand, gray to tan, slightly clayey; contains sparse organic
material_--_____-_______-_______-___-_____-_-^____________ 3 0Middle Miocene, Hawthorn formation:
A6. Limestone, white to light-tan, sparsely to slightly sandy and clayey, soft, dolomitic; contains rounded pebbles of white to very light gray very calcareous clay and a trace of tan, brown, and black phosphate nodules that are mostly sand size; upper contact sharp and undulating. _____________________________________ 3
A5. Limestone, white to light-tan, very sandy (fine to medium grained), sparsely clayey, hard, dolomitic; contains sparse rounded pebbles of white pure limestone and a trace of sand-size phosphate nodules __ ______________________________________________ 3
A4. Limestone, white to light-tan, very sandy (fine to medium grained), sparsely clayey, dolomitic; contains abundant patches of nearly pure carbonate and a trace of brown, black, and amber sand-size phosphate nodules. __-__-_-___-_____---____________ 3
A3. Limestone, white to light-tan, very slightly to very sandy (fine to very fine grained), slightly clayey, dolomitic; contains abundant patches and fragments of gray calcareous clay with phosphate nodules_______---__-----------------_-------_---_ 6
A2. Limestone, white to light-tan, sandy (fine to medium grained), slightly clayey, hard, dolomitic; contains abundant patches of very sandy carbonate and pure carbonate, and sparse black, brown, and gray sand- to pebble-size phosphate nodules. _ 6
Al. Limestone, white to light-tan, sandy (fine to medium grained), slightly clayey, locally porous, dolomitic; contains sparse small fragments of white pure limestone and sparse black, brown sand- to pebble-size phosphate nodules; Potamides, n. sp. aff. P. hillsboroensis Heilprin, Chlamys sp. cf. C. sayanus Ball, Cordztim sp___--_-___. ------------------------------------ 1 6
Total exposure..------------------------------------ 6 3Base of exposure.
STRATIGRAPHY 41
Limestone of the Hawthorn formation is also described in the log of core hole G16 (p.103), and in the list of Hawthorn localities. Ex posures of the upper limestone unit are present at localities 98 and 99 and elsewhere in Manatee and Sarasota Counties.
The sand and phosphorite units of the Hawthorn formation generally consist of an alternation of brown to green clay, sand, and sandy clay. Clay predominates in the phosporite unit and sand predominates in the sand unit. Gray green nearly pure waxy clay beds are present at some localities (figs. 12 and 13). Beds pinch out or merge laterally into different lithologies within a few hundred feet. The phosphate is- similar to, but locally more abundant than that in the limestone units. Many of the nodules are leached and soft, however, and in places they have been completely removed, leaving an indurated rock full of small vesicles. Weathering has locally produced a white sandstone cemented by secondary aluminum phosphate minerals. In some areas
EXPLANATION
Contact between lithologic units
Clayey sand Slightly phosphatic Slightly sandy clay clayey sand
10 20 Feet
Fossils
FIGURE 12. Diagrammatic sketch showing stratigraphic relations of Hawthorn formation, undifferentiated Pliocene and Miocene strata, and Quaternary sand at locality 83 (northwest side of railroad cut, about 0.5 mile northwest of railroad station at Kathleen), SWH sec. 17, T. 27 S., R. 23 E., Polk County.fcFla. Petrographic properties of samples are given below.
Sample
83B6-. .-.- ...83B5. ..-.....83B4-...........83B3-..... ...83B2.. .... ...83B1._..._._..__
SO
1.11.81.11.9.6
2.8
B
Md
0.12.12.22.23.19.19
So
1.211.181.361.471.301.25
P«
0.27.24.50.58.40.42
Sample
83A5.. ..........83A4-. .........83A3............83A2............83A1. ...........
A
SO
2.11 01.33.4.4
Md
0.15.13.22.24.18
So
1.411.241.481.371.35
P«
0.32.29.46.56.47
SO Ratio of sand to clay.Md Median diameter of sand, in millimeters.So Sorting coefficient of sand.P« Fifth percentiJe, in millimeters.
42 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
this process is accompanied by oxidation of the iron in heavy minerals, which produces brilliant orange or red-brown iron staining and zones of hardpan.
EXPLANATION
Contact between lithologic units
Base of red-soil zone
Sand Red-soil zone Clayey sand
10 9 10 20 Feet
Slightly sandy clay
FIGURE 13. Diagrammatic sketch showing stratigraphic relations of Hawthorn formation and Quaternary sand at locality 13 (northwest corner of claypit on State Highway 579, 0.5 mile north of Mango), NWJ4 SWH sec. 3, T. 29 8., R. 20 E., Hillsborough County, Fla. Petrographic properties of samples are given below.
Sample
13A6--. 13A5.. .... 13A4-. .... 13A3... ____ .13A2--... .13A1- ~
SO
1.33.21.5.2
2.3.1
A
Md
0.18.18.14.13.16.11
So
1.491.521.381.36i:391.57.
Ps
0.46.47.42.29.32.37
. Sample
13B5 _____ ..13B4-. ..........13B3- .... .13B2_. ..........13B1. ...........
B
SO
2.4.3
3.3.1
2.6
Md^
0.16.20.15.10.14
So
1.441.561.171.361 9*
PJ
0.34.45.22.2229
SO Ratio of sand to clay.Md Median diameter of sand, in millimeters.So Sorting coefficient of sand.Ps Fifth percentile, in millimeters.
STRATIGRAPHY 43
The sand and phosphorite units are best exposed around Dade City (Iocs. 60, 61, 68, and 71) in Pasco County, and in some of the northern phosphate mines such as Sydney (loc. 39) Tenoroc (loc. 73), and Pauway (loc. 75). A section (loc. 83) near Kathleen, typical of the less phosphatic sand unit, is given below and in figure 12.
Locality 88, SW% sec. 17, T. 27 S, R. S3 E., railroad cut, 0.5 mile northwest of railroad station at Kathleen, Polk County, Fla.
[Numbers are sample numbers]Approximate
I thicknessQuaternary: ^ in)
B7. Sand, tan, loose_-_-----_---______-____________-___-_____ 1 10Undifferentiated Pliocene and Miocene:
B6. Sand, gray, orange-brown iron-stained, fine-grained; contains a trace of muscovite...____..._________._______.____.__..__ 6
B5. Sand, light-gray, mottled yellow-orange iron-stained, fine grained, clayey to slightly clayey; contains a trace of mus- covite__-----_-----_-_-_-_---_---_----_----_-___-.________ 1 3
Middle Miocene, Hawthorn formation:B4. Sand, light-tan to light-gray, local orange iron-stain, fine- to
medium-grained, locally vesicular; contains a few very thin lenses of dark-gray clay, a trace of phosphate nodules and soft white phosphatic (?) patches, and fossils of white soft tripoli: Ostrea normdlis, Dall, Chlamys sayanus Dall; upper and lower contacts undulating______-____-_________________ 6
B3. Sand, light-gray to light-tan, yellow-brown. iron stain at top, fine- to coarse-grained, slightly clayey; upper contact sharp. _____ 1 4
B2. Clay, gray-green, dark-red-brown iron stain at top, slightly sandy (fine- to medium-grained), waxy, blocky fracture; contains sparse small lenses of gray slightly clayey sand, and trace of sandstone fragments cemented by aluminum phos phate^); upper contact undulating________________________ 1 6
Bl. Sand, light-gray-green to tan, slightly iron-stained at top,fine- to medium-grained; upper contact sharp._____________ 1 0
Total exposure_-_____--_---_-_-___--__-___----_----_ 7 11 Base of exposure. .
44 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
The following section, typical of the lithology of the phosphorite unit, was exposed in February 1954.
Locality 75, Pauway mine, American Agricultural Chemicals Corp., section near center of sec. S2, T. 28 S., R. 24 E., Polk County, Fla.
[Numbers are sample numbers]Approximate
thicknessQuaternary: (/' in)
C8. Sand, tan, loose_______--____-___-__--___-_-___-___--____ 4 0Undifferentiated Pliocene and Miocene (Bone Valley? formation):
C7-. Sand, light-gray to gray, mottled red-brown at top, fine- to medium-grained, clayey to slightly clayey; contains a trace of sand-size phosphate nodules; upper contact sharp___ 3 6
C6. Clay, light-gray, very sandy (fine- to coarse-grained); contains a trace to abundant white soft sand- to granule-size phos phate nodules__--_--__---_---_-__-----___-____________ 2 0
C5. Clay, light-gray-green with yellow iron staining, sandy (me dium- to fine-grained); contains very thin lenses of sand with a trace of phosphate nodules; upper contact sharp _________ 1 0
C4. Sand, light-gray-green, fine- to medium-grained, clayey, inter- lensing with sandy clay; contains patches of white soft phos- phatic(?) clay___________________________ 1 6
C3. Clay, light-blue-green, brown iron stain at top, sandy (fine- to medium-grained), waxy; contains a trace of white, gray phosphate nodules__--_-___---_-______-________________ 1 6
Middle Miocene, Hawthorn formation (phosphorite unit):C2. Sand, light-gray-green, locally iron stained, medium- to fine
grained, slightly clayey; contains white, gray, tan sand- to granule-size phosphate nodules and, at top, patches of white soft phosphatic clay; upper contact sharp, undulating______ 2 0
Cl. Clay, white, tan to light-gray, slightly sandy, locally calcareous at base; contains abundant white, gray sand- to pebble-size phosphate nodules____-------__-----___ -___-_---___ 11 0
Total exposure_-__-_-_-_-_______________________ 26 6Base of exposure.
Other exposures where sand and clay beds assigned to the Hawthorn formation are exposed are shown in figures 13, 14, and 15.
Lithology typical of the phosphorite unit and the sand unit was also found in core holes in Hillsborough County (fig. 16 and logs of core holes).
Quartz sand in the Hawthorn formation is mostly fine grained but ranges from very fine to medium grained with a trace of coarse grains. The sand is irregularly distributed and is clear and angular to sub- rounded, except for some of the larger grains which are frosted and well rounded. Petrographic data for the formation are summarized in figures 4-9. Limestone of the formation averages about 20 percent insoluble material. The formation, in samples analyzed, has a range
STRATIGBAPHY
A
45
3~ S-
UJ§ 30-
sCO
UJ
O m < 25-
tUJu.
Water level .
~-
-err
Soft limestone _ boulder
.'.' .':'; ' :'
>>/^0
n&^^6: 'r'.v.v:
tt!3^£
sH
I N
Qs, Quaternary sand
A7 Mh, Middle Miocene, Hawthorn _^AJL_^^formation, clayey sand
f\ >J ^rYT 7
A3
iJA2
-^ ^^
Mtv Tampa fossils^"" Lower Miocene, Tampa limestone,
soft limestone, sand, clay, and chert
EXPLANATION
Contact between lithologic units Dashed where inferred
Sand Clayey sand Chert Calcareous sandy clay
Clayey limestone
10 Feet
FIOURE 14. Diagrammatic sketch showing stratigraphic relations of Tampa limestone, Hawthorn forma tion, and Quaternary sand at locality 24 (northeast comer of sandpit), NE^ sec. 33, T. 28 8., R. 19 E., Hillsborough County, Fla. Petrographic properties of samples are given below.
Sample
24A7 ... ...24A6- .....24AS .........24A4 >..... _ ...
SO Md
0.18.13.16
So
1.391.291.35
Ft
0.35.30.37
Sample
24A3.. . .........24A2.. ..........24A1» ........
SO
1.3
1.0
Md
0.16.14.12
So
1.321.241.23
P«
0.29.24.19
SO Ratio of sand to clay.Md Median diameter of sand, in millimeters.So Sorting coefficient of sand.Pj Fifth percentile. in millimeters.«Chert.> Insoluble residue.
of sand median diameter from 0.09 to 0.28 mm and the median for all samples is 0.175 mm. The sand is well sorted but the sorting coeffi cient shows a range from 1.10 to 1.63. Fifth percentile (P6) values are consistently high in sand of the Hawthorn, even when the median diameter is low; P6 ranges from 0.20 to 0.58 and the median is 0.355 mm. The properties of the units of the Hawthorn composed of clay and sand are similar to those of the limestone units, but in the non- calcareous beds the sand is slightly coarser and not quite as well sorted.
501224 5& 4
46 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
EXPLANATION
Contact between lithologic units
Base of red-soil zone
Sand Clayey sand ; Sandy clay
25 0 25 50 75 Feet
I a a aChert
IOURE 15. Diagrammatic sketch showing stratigraphic relations of Tampa limestone, Hawthorn forma tion, and Quaternary sand at locality 6 (east side of readout about 100 feet south of railroad bridge),
sec. 19, T. 28 8., R. 20 E., Hillsborough County, Fla. Petrographic properties of samples are given below.
Sample
6A7.. ..6A6- - .... .6A5- ..... .6A4. ... -
A
SO
1.93.2.8
3.8
4.
Md
0.16.14.14.10
So
1.431.301.261.23
Ps
0.41.36.19.16
Sample
6A3. ...6A2>-__ ...6A1... .
A
SO
1.0
.8
Md
0.09
.09
So
1.37
1.20
PS
0.23
.18
SO Ratio of sand to clay.Md Median.diameter of sand, in millimeters.So Sorting coefficient of sand.Ps Fifth percentile, in millimeters.i Chert.
47
Sea level-
Qs, Quaternary sand
PMsc, Pliocene and Miocene, 10 undifferentiated, sand and clay
Mt, Lower Miocene, Tampa limestone
(J)s, Oligocene, Suwannee limestone
Geologic logs of these holes are given In the text; location of the sections is shown on pi 2
PMsc, Pliocene and Miocene, undifferentiated, sand and clay
EXPLANATION
Contact Dashed where Inferred
Top of first limestoneRadiometnc log, 5-foot
averages, hundreds of counts per minute
1 0 1 Milo
Gil : Number of core hole
NL Not logged radiometrically
FIGURE 16. Sections through core holes in northeastern Hillsborough County, Fla.
Heavy minerals are present only in trace amounts in the limestone of the Hawthorn, but are concentrated in the sand and phosphorite units, presumably by weathering. In general the percentages of garnet and staurolite in the heavy fraction are about equal, each comprising about 25 percent. Some heavy-mineral fractions contained as much as 50 percent garnet. The percentage of staurolite remains relatively constant, however, and most samples contain more than twice as much as the Tampa limestone. Opaque minerals range from 10 to 50 percent, partly due to the inclusion of dark isotropic phos phate particles in this group. Other heavy minerals present, in amounts generally less than 10 percent, are epidote, kyanite, rutile, tourmaline, sillimanite, sphene, topaz, zircon, and muscovite.
48 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
Three chemical and three spectrographic analyses of different- materials from the sand unit of the Hawthorn formation are given in the table below.
Chemical and spectrographic analyses of samples of the sand unit of the Hawthorn formation, southeastern Pasco and northeastern Hillsborough Counties, Fla.
Partial chemical analyses
Locality, field, and laboratory sample
No.
53B; 115961
60A1; 115962
60A2; 115963 (split from 60A1)
Material
sandy.
very sandy; contains sparse fragments of sandstone ce mented by aluminum phos phate.
cretionlike lumps; contains cavities lined with an alu minum phosphate mineral.
PsOt
0.1
1.5
18.2
CaO
0.22
.10
.6
Percent
AhOj
9.2
16.1
20.7
FeiOs
3.29
5.44
1.06
MgO
0.1$
1.55
.85
Spectrographic analyses
Locality, field, and laboratory sample No.
9A2; 115721.
61A2; 115751
6102; 115749..
Material
Sand, tan to brown, con tains sparse fragments of sandstone cemented by al- uminum»phosphate.
Sand, violet-gray, slightly clayey, iron-stained.
Sand, gray, slightly clayey; contains lumps of hardpan and silicifled corals.
Elements in percent range
99-10
SI.....
Si
Si
9-1
AL... _
Al ..
Al, P..
0.9-0.1
Fe, Mg, P, Ca.
Fe, Ti, Mg..
Fe.Mg, Ti, Ca.
0.09-0.01
Ti, Sr, Cu, Or, Ba, Na, Ni, B,Co.
Cu, Cr, Ca, Sr, Ni, B, Ba.
Cu, Cr, Ba, Ni, B, Mn, V,
, Sr.
0.009-0.001
Mn, Mo, Pb, V, Y, Ga, Sn, Zr.
Mn, Mo, Ga, Sn, Zr, Pb. V, Y.
Mo, Zr, Ga, Pb, Sn, Y.
POST-MIDDLE MIOCENE BOCKS
Formations younger than the Hawthorn were not mapped, although some samples of the later formations were mechanically analyzed. Ketner and McGreevy (1959) and Bergendahl (1956) describe these formations in detail. Some of these rocks are described briefly here.
BONE VALJLEY FORMATION
The Bone Valley formation (Matson and Clapp, 1909, p. 138-141)^ which overlies the Hawthorn, is the source of a large part of the phosphate mined in the land-pebble district. Its exact age has never been proved, partly because of a lack of invertebrate fossils, but according to Simpson (1930, p. 184; 1933, p. 91) vertebrate remains indicate that it is Pliocene in age. Simpson (1930, p. 184-185) lists 13 species of vertebrates from the Bone Valley formation, 10 of which he says may range in age from late Miocene through early Pliocene, 1 of which he says occurs elsewhere only in the upper Miocene, and 1
STRATIGRAPHY 49
of which he says is typically early Pliocene in age, but whose age xange is undefined. He summarizes the fauna as follows
The evidence of the land mammals * * * indicates approximate equivalence with the upper Snake Creek or the Republican River. With this relative age (established, it is of little consequence whether it be called late Miocene or early Pliocene. At present the consensus seems to be that the Republican River and equivalents are referable to the lower Pliocene.
Simpson then points out that the marine mammal fossils of the Bone Valley have been described as being not later than late Miocene in age. He resolves this discrepancy by suggesting that the age or identification of the marine mamm.al fossils may be in error. In a subsequent publication (Simpson, 1933, p. 91) he lists the Bone Valley as Pliocene in age. In our opinion the question of the age of the Bone Valley is far from settled.
The formation consists of gray and green sand and clay beds containing, in places, as much as 75 percent phosphate nodules. The sand in these beds consists of quartz and phosphate nodules which, when taken together, are rather poorly sorted as a rule. Stratification is poor in many exposures. The quartz sand has size properties very much like those of the Hawthorn, but the Bone Valley seems to show poorer sorting and more variation from sample to sample in a vertical section. In samples analyzed the medians of P5, median diameter, and sorting coefficient are 0.39 mm, 0.18 mm, and 1.42, respectively.
Weathering has made the contact between the Bone Valley forma tion and residue of the Hawthorn formation difficult to locate in exposures and impossible in drill holes. Traditionally, noncalcareous beds mined for phosphate ("matrix") in the land-pebble district have oeen referred to the Bone Valley regardless of- their age. A contact occasionally seen in the phosphate pits is an undulating unconformity that is locally transected by the base of a leaching profile. Whether or not this unconformity coincides with the contact between the Hawthorn and Bone Valley formations is a matter of conjecture in our opinion, but it is certain that much of the material mined for phosphate, particularly in the northern part of the district, is actually residuum of the Hawthorn formation.
UNDIFFERENTIA.TED MIOCENE AND PIJOCENE ROCKS
Above the Hawthorn formation in Polk and Hillsborough Counties are beds of sandy clay which were not differentiated in this work. Some of these beds may be of Bone Valley age, others are probably correlative with a clayey sand described by Ketner and McGreevy (1959).
These rocks closely resemble the clay and sand beds of the Hawthorn
50 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
and Bone Valley, but generally have less phosphate and locally contain abundant fine-grained muscovite flakes (loc. 83). Analytical data for rocks of post-middle Miocene, pre-Quaternary age, are summarized in table .4.
WEATHERING
Throughout subtropical Florida the climate, topography, drainager vegetation, and rock types are very favorable to the formation of residua. The weathering is largely lateritic and iron- and alumina-rich zones are typically developed. Where the parent material is favorable secondary chert and aluminum phosphate zones commonly form.
The typical weathering profile begins at the surface with several feet of loose pure white or tan quartz sand which becomes clayey and orange or red downward. Iron and alumina hardpan, aluminum phosphate, and chert nodules are common at the base of this zone. Beneath the hardpan or chert is a zone of generally blue or gray-green clay and sandy clay locally containing calcium phosphate nodules. At the base of the profile is a thin zone of slighly calcareous sandy clay that grades rather abruptly into limestone. The profile is thus principally one of decreasing solubility upwards. The depth of such leaching exceeds 50 feet in some places in this area.
Beds of clay and sand obviously weathered from limestone are present at many localities in the area mapped. In a few places such beds contain chert lenses with fossils. Usually, however, it is difficult to determine whether an unfossiliferous sandy clay above limestone at an exposure is residual from the limestone, is a virtually unweathered bed of the formation, or belongs to a formation of later
Several criteria may be used to help ascertain the relations under such conditions. One of the most indicative of these is the formation of chert. Leith (1925, p. 513-523) pointed out that secondary silica on erosion surfaces develops on a variety of rocks, of which limestone and dolomite are said to be the best sites for surficial silicification. That most of the chert seen in exposures in Florida is an epigenetic replacement of limestone is indicated by (1) the massive porcelanic, vitreous appearance of the chert, (2) the irregular shape of the masses, (3) the inclusion within chert of calcite grains and patches, and pockets of calcareous material, and (4) the inclusion of silicified fossils within the chert. MacNeil (oral communication, 1954) noted that only the protruding parts of mollusks in the wall of a limestone sinkhole in northern Florida were silicified, the part of the shells remaining in the limestone was carbonate.
The abundant examples of replacement of limestone by chert, of silicified originally calcareous fossils in clay beds, and the texture
WEATHERING 51
of the chert itself lead the writers to conclude that chert, at least in this part of Florida, forms in significant amounts only in the presence of limestone; therefore its occurrence as a fairly continuous zone in a deeply weathered section is good evidence, barring reworking, that the bed containing the chert was originally calcareous.
One of the best examples of a chert bed in a weathered section is at locality 6 (fig. 15). This chert contains fresh-water plant seeds which suggest that the chert has replaced a fresh-water limestone bed.
The presence of unreworked silicified head corals, such as Sidera- straea, in a weathered section is also evidence that the beds on which they rest were originally limestone, if it is accepted that growing corals can survive only in a mud-free environment.
Solution textures are usually obliterated by prolonged weathering and complete removal of carbonates, but in clay and sand features such as crenulated bedding are good evidence of solution of limestone below the contortions.
SUWANNEE LIMESTONE
Only small amounts of residual clay have been seen on top of the Suwannee limestone in this area. Weathering could not produce significant amounts of residuum because the formation contains very little insoluble material. A possibility remains, however, that a clay residuum overlying a pure limestone like the Suwannee may be a result of replacement plus concentration by weathering.
The chert in the Suwannee limestone is almost entirely surficial and shows very irregular contacts with the replaced limestone. Chert is widespread on top of the Suwannee, particularly in northern Hillsborough and southern Pasco Counties where the formation crops out. Some of the chert has rinds of porous white and brown tripoli, an indication of intense leaching, possibly brought about by removal of the surficial protecting cover of sand and clay.
TAMPA LIMESTONE
Effects of weathering upon Tampa limestone are especially well shown in the Tampa area by silicification, contortion of bedding, and clayey residues.
The presence of chert in the Tampa limestone is similar to that in the Suwannee, but massive blanket zones of chert are not so common in the Tampa. Commonly secondary silica in the Tampa occurs as angular or platy masses of chert, as thin fissure fillings, or as silicified fossils. Secondary silica in at least one of the above forms was found in more than half of the exposures of the Tampa listed in this report, in about 75 percent of the core-drill holes that reached the
52 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
formation, and in the majority of wells logged of the Tampa. Figures 14 and 15 illustrate two occurrences of chert in exposures. Silicified fossils are present at both these localities. At locality 24 (fig. 14) Tampa fossils (table 2) are present hi chert lenses. At locality 6 (fig. 15) Tampa mollusks (table 2) are present as soft tripoli; silicified Siderastraea corals are present, and a silicified bed, partly tripoli, contains fresh-water plant remains. At Ballast Point (loc. 2) the "silex bed" contains numerous beautifully silicified fossils.
The effects of limestone solution on bedding can be seen at locality 6 (fig. 15). A clayey bed at the top of the Tampa has crenulations with amplitude as much as 4 feet, and in short lateral distances varies from a few inches to a foot and a half thick. Lower beds in the exposure are similarly distorted to a lesser degree.
At two exposures (24, 25) of the Tampa limestone that illustrate the residua problem, masses of soft limestone as much as 3 feet in diameter are surrounded by clay. These "boulders" are pierced by thin seams of calcareous clay, but the contact between limestone mass and surrounding clay is quite sharp. A sketch of the stratigraphic relations at locality 24, typical of super-Tampa weathering, is given in figure 14. Insoluble-residue analysis of a sample (24A1) of the mass of limestone and a raw sample (24A2) of.the clay immediately adjacent showed that the sand has median diameters of 0.12 and 0.14 mm, respectively. X-ray analysis 3 of the clay fraction of these two samples revealed quartz, orthoclase, montmorillonite, and pseudo- wavellite hi both the limestone (24A1) and clay (24A2), plus wavellite and apatite in the clay. Spectrographic analysis of raw splits of the two samples detected no phosphorus whatever in the limestone, but O.OX percent was found in the clay.4 The data, both petrographic and analytical, suggest that the clay is residual from the limestone, and that the weathering has concentrated phosphorus in the clay. Units 24A3, a very slightly calcareous sandy clay, and 24A5, a pure white sand,, are lenticular and both underlie ledges of chert (24A4, 24A6) that contain lower Miocene fossils (table 2) and small amounts of very fine grained sand. Unit 24A7, a red clayey sand, is uncon- formable upon units 24A3-24A6 and has petrographic properties that correspond closely with those of the Hawthorn formation. Therefore, we believe that this is an unconformable Tampa-Hawthorn contact, .and that units 24A3 and 24A5 represent solution cavities filled by materials from both formations.
A comparison of two stratigraphically equivalent samples of rela tively pure limestone of the Tampa, one virtually unweathered, the other moderately weathered, is given below. The two samples were
> Informal analysis by R. G. Petersen, U.S. Geological Survey. * Laboratory nos. 115724 and 115725.
WEATHERING 53
taken from the wall of a sinkhole from points about 15 feet apart laterally. Note that the petrographic data from the two samples agree very closely, and that the percentages of carbonate obtained by calculation from the chemical analyses are close to the percentages of soluble material obtained by insoluble-residue analysis. The percentage of insoluble materials has increased nearly 4 tunes in the weathering, which removed about 25 percent of the carbonate. The ratio of sand to clay remained almost the same, however. A bed 10 feet thick of this limestone would yield, after weathering removed all carbonate, at most about 1 foot of residue, if changes in porosity are ignored. A possibility remains, however, that as the carbonate is removed it may be replaced by clay minerals under special condi tions of weathering, but if this occurs then the ratio of sand to clay should decrease in the replaced sample. On the other hand, if one assumes that the clay beds, so commonly found above limestone in this area, are.strictly residual then it is necessary to postulate the existence of 5-10 feet of original limestone for each foot of residue.
Other changes in composition shown by the analyses below are slight. The percentage of A1203 increases in proportion to the increase in clay, and there is a slight increase in Fe2O3 in the weathered sample.
Comparison of siratigraphically equivalent samples of fresh and weathered limestone of the Tampa limestone from locality 19, Hillsborough County, Fla.
[Laboratory Nos.: 19A2,115934; 19B1,115938]
Fresh (19A2)
Weathered (19B1)
Partial chemical analysis. In percent
P.O...... .--. .-. --. ..-.--.- . .- - .- .OaOOjAltOi..... ............... ... ............... ................. ...Fe.0..... ... ___ ... __ ... _ ................ ... ...... ......
Total.................................. _. _ ..
0.390.1
.8
.271.6
93.07
0.367.32.8.52
1.5
72.42
Insoluble-residue analysis, in percent
Insoluble material:
Clay and silt __________________ ___ . ......Soluble material ___________________ .. _ . ___ _ ......
Total... ._..... ..-......._.__ ... .- .--... _.- __ _
3.25.7
91.0
99.9
12.6 22.1
65.0'
99.7
Mechanical analysis
Sorting coefficient of sand ___ ..............Fifth percentile ________________ ._ .. _____ millimeters..
0.560.0861.380.22
0.570.085-1.330.23
54 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
As the Tampa contains only small amounts of phosphate nodules in most places, highly phosphatic residues are not commonly formed. However, radiometric logs of many of the drill holes indicate local zones of abnormal radioactivity within the Tampa (figs. 2, 3, and 16). Most of the peaks of radioactivity in the Tampa are at the top of the formation, although in Pasco County a secondary peak was noted at the base. The litholdgic logs of these core holes show" that the radio activity at the top of the Tampa is due to the presence of aluminum phosphate cement formed by leaching of calcium phosphate nodules. The radioactive zone at the base of the Tampa in Pasco County ap pears to be due to unleached colloidal apatite. In the core holes southeast of Dade City weathered material extends to a depth of at least 100 feet, judging from the presence of secondary phosphate minerals at the top of the Tampa, but the presence of calcium phos phate at the base of the formation in these holes suggests that leach ing has been absent or much weaker toward the bottom of the forma tion. In core holes Gill and G112 noncalcareous lower Miocene clayey sand rests directly upon unleached Suwannee limestone.
HAWTHORN FORMATION
Of the limestone formations described in this report, the Hawthorn is the one most affected by weathering, primarily because it is close to the surface in much of the area. Weathering has resulted in clayey sand of two types, as discussed in the section on stratigraphy.
In the land-pebble phosphate district weathering of limestone of the Hawthorn formation has produced a phosphatic residuum (phosphorite unit) that is often indistinguishable from, and mined with, the over lying Bone Valley formation. In order to map these beds it would be advantageous to regard phosphatic clayey sand and limestone phases &s separate mappable units regardless of age. The objection is then raised that such a map would show only a leaching profile crosscutting stratigraphic units. We have therefore mapped two units (pi. 1), limestone and clayey sand, of the Hawthorn formation, but the Bone Valley formation and noncalcareous residua overlying limestone of the Hawthorn are not shown.
The Hawthorn formation exhibits three general zones of weather ing. The first and weakest zone is that commonly seen in the bottoms of the phosphate pits where the limestone is soft, yellow, and has a marly or chalky appearance. This type of limestone is only a few feet thick in most places, and is almost invariably dolomitized; it has poorly preserved fossils, scattered phosphate nodules, and blotchy areas of alteration.
The second zone of weathering of the Hawthorn lies above the lime stone and consists of noncalcareous to calcareous greenish-gray clayey
. WEATHERING . ; 55
-sand with abundant phosphate nodules. The material is apt to be .structureless but in some places contains wavy distorted beds of green clay and occasional lenses of incoherent phosphatic sand. This lithol- ogy represents an intermediate stage in weathering where leaching has been strong enough to remove most of the carbonate and to concen trate, but not otherwise affect, the calcium phosphate nodules.
The third zone of weathering of the Hawthorn formation is best exposed in northern Polk (fig. 12) and Hillsborough Counties (fig. 13) and eastern Pasco County, but is rarely seen in the phosphate pits. It consists of loosely cemented brown to red clayey sand, with local hardpan layers made up of iron oxide and aluminum phosphate ce mented sand. Distorted green waxy clay beds are common, and an occasional altered calcium phosphate nodule may be present. This lithology represents a severe stage of weathering in which carbonate, if originally present, has been completely removed, calcium phosphate has been altered to form concretions and hardpans of aluminum phos phate, and some of the heavy minerals have been oxidized to produce iron staining.
The scarcity of secondary chert in the Hawthorn is notable. There are occasional silicified fossils or small chert fragments in weathered exposures of the Hawthorn, but no massive chert like that of the Suwannee and Tampa limestones was found anywhere in the formation in this area. The reason for the scarcity of chert in the Hawthorn is not clear, but a partial answer may be that impurities in the lime stone, perhaps magnesium or phosphorus, inhibit chert formation. If this is true, then the presence of abundant chert in a weathered outcrop of clayey sand may be taken as evidence of the former presence of a rather pure limestone.
POST-MIDDLE MIOCENE ROCKS
Weathering of post-middle Miocene rocks was not studied in detail. In general, however, features of weathering of upper Miocene and Pliocene beds appear similar to those of the Hawthorn, thus adding to the difficulty of distinguishing them from deposits of middle Miocene age.
At locality 1 (Sixmile Creek), calcareous well-preserved shells of Pleistocene age are found in a sand resting upon Tampa limestone. Everywhere that Pleistocene shell beds were seen they seemed to be little altered in spite of their proximity to the surface.
DATE OP WEATHERING
The exact age of the major weathering period in west-central Florida is difficult to determine. The ubiquitous surficial sand gen erally thought to be Pleistocene in age (MacNeil, 1949; Cooke, 1931)
56 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
may be seen (fig. 13) to rest unconfonnably upon a red-soil zone or zones developed principally on Miocene or Pliocene rocks. Pleisto cene (Mansfield, 1937, p. 22) sand beds of the Pamlico terrace in the Tampa Bay area (loc. 1) are within a few feet of the surface, yet they contain calcareous, virtually unleached Pleistocene shells. At localities 1 and 26 the basal part of the Pleistocene rests directly upon Tampa limestone and contains numerous silicified shells and corals reworked from the Tampa limestone. No Pleistocene shells have been found in this area in surficial sand above the Pamlico terrace, which is about 30 feet above present sea level.
As the aforementioned red-soil zone apparently transects all exposed formations older than Pleistocene, the evidence indicates that a period of major weathering occurred in late Pliocene or early Pleistocene, probably at a time when sea level stood lower than it does today.
We believe, however, that there is evidence which suggests that earlier periods of weathering are represented in the area; some of these, we contend, occurred at the end of, and possibly during, early Miocene deposition. The evidence is as follows: (1) wavellite, a secondary phosphate mineral, is present in clayey sand between beds of limestone in the Tampa, and secondary peaks of radioactivity occur locally at the top of the Tampa in well logs; (2) a widespread zone of silicification is present across the top of the limestone of the Suwannee and Tampa, chert zones of possible secondary origin are present within the Tampa, and virtually no silicification is present on top of Hawthorn lime stone; (3) leaching reaches to extreme depths in some areas (over 100 feet in the Dade City highlands); (4) exposures of the Tampa-Haw thorn contact show that crenulations due to slumping from solution of Tampa limestone are not always present in material of probable middle Miocene age (fig. 15). The fact that an unconformity exists between Tampa limestone and the Hawthorn formation also supports this view.
PETROGRAPHIC COMPARISONS
The petrographic data obtained in laboratory work are summarized graphically in figures 4-9. It is only necessary to point out the salient features shown by these graphs.
First, and probably most significant, is the general increase in the size of quartz sand from the Suwannee limestone through the Haw thorn formation. The same progression is apparent, though not so strong, in the sorting and percentage of quartz sand. The Hawthorn, for example, has poorer sorting and slightly more sand-size material than the Tampa limestone. However, the Tampa contains slightly more clay and silt than the Hawthorn formation. In all parameters determined the Hawthorn shows more variability than the older
PETROGRAPHIC COMPARISONS 57
rocks, and it contains more grains of sand that are conspicuously coarser. The latter characteristic is recognizable and useful in the field.
Figure 7 shows that rather sharp changes in properties occur at or near formation contacts, and that the data from well samples agree in trend, though not always in absolute value, with those obtained from exposures.
Figure 7 also shows some relations between the petrographic char acteristics themselves. The graphs of median diameter and fifth percentile values maintain a close parallelism throughout the log. In addition, there seems to be a relation between the sorting coeffi cient and fifth percentile and median diameter values. With a few exceptions, below 140 feet the two show a direct relation, but above this point they show an inverse relation. In other words, below 140 feet the coarser the sand the poorer the sorting as compared to adja cent samples, and above 140 feet the coarser the sand the better the sorting becomes.
All data are condensed in table 4 to give a general picture of the petrography of formations in this area. Note in particular the similarity in size characteristics between the Hawthorn and overlying formations.
TABLE 4. Summary of medians of petrographic characteristics for the Ocala, Suwannee, and Tampa limestones, the Hawthorn formation, and rocks of posl- middle Miocene and pre-Quaternary age, west-central Florida
[Phosphate nodules are excluded]
Rocks of late Miocene or Pliocene age » ... Hawthorn formation. ___________Tampa limestone ______________
Ocala limestone' ..........................
TotalInsoluble 'material(percent)
100 1920
32
Quartzsand'
(percent)
64 141251
Mediandiameter
(millimeter)
0.17 .176.12.10
1 .10
Fifthpercentile
(millimeter)
0.38 .355.22.15.26
Sortingcoefficient
1.40 1.331.221.191.37
1 For samples 50 percent or more soluble, Hawthorn and older formations.s Includes rocks of probable Bone Valley age and other rocks of late Miocene or Pliocene age that Im
mediately overlie the Hawthorn formation. ' Average values of 7 samples.
It should be reemphasized that the chief value of the insoluble residue-mechanical analyses lies not in absolute figures for particular samples, but in comparisons between formations based upon uniform analysis of many samples.
Clays of the Tampa and Hawthorn show some relations that deserve further investigation. The dominant clay minerals seem to be mont- morillonite in the Hawthorn and illite in the Tampa. Attapulgite occurs in both formations in association with high MgO content; it
58 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
is found in samples of the Tampa that contain land or fresh-water fauna, and it is common in the Hawthorn at the top of the formation..
GEOLOGIC HISTORY
STRUCTURE
Tertiary structural deformation in Florida was confined to minor upwarping, subsidence, and faulting of small displacement. The Florida peninsula has been a relatively stable area throughout most of geologic tune. No deep ocean basin deposits are known (Vernon, 1951, p. 64).
The Tertiary formations normally dip a few feet per mile in a southerly direction. However, as most of these formations are less- than 150 feet thick even a small displacement can affect the outcrop pattern. Several gentle domes or arches are present in the Florida peninsula and cause local variations in the dip of the formations.
OCAJLA UPLIFT AND DISTRIBUTION OF MIOCENE ROCKS
The dominant mid-Tertiary structural feature of west-central pen insular Florida is the "Ocala uplift" (fig. 1), a gentle arch that ex tends from Polk County northwest to the Georgia border. Most of the subordinate structural features in west-central Florida appear to be related to this arch. The crest of the Ocala uplift follows a line from northern Polk County through Lake, Sumter, Citrus, Marion, and Levy Counties. In much of this area Eocene rocks, including the Avon Park limestone, are exposed or are near the surface and are covered by a thin veneer of Miocene and later sediments. The Tampa limestone and older rocks were involved in the deformation that paralleled the axis of the arch, and formations younger than the Tampa may have been affected slightly. Vernon believes (1951, p. 62) that the evidence favors placing the major structural movements associated with the uplify ini early Miocene time.
Verno'n contends that the Miocene formations never extended com pletely across the Ocala uplift, but pinched out against it. His con clusions are based partly upon an effort to find a source for phosphate in the Hawthorn formation. He thought that the most logical source for the phosphate would have been a land mass centered on the crest of the Ocala uplift in early Miocene tune upon which large deposits of guano and phosphatized limestone accumulated. The erosion of this material, he theorized., contributed the phosphate for the Haw thorn deposited around the uplift. The theory is an interesting one, but the nondeposition of Miocene rocks on the crest of the uplift seems untenable for several reasons.
The Ocala uplift is adjoined on the north, northeast, and southwest by a discontinuous arcuate belt of outcropping Tampa and Haw-
GEOLOGIC HISTORY 59
thorn formations. The formations at most places are higher than, and dip away from, the area which they encircle. The base of the Hawthorn in much of this belt is from 10 to 50 feet higher than the present surface of Eocene rocks on the crest of the uplift. In the area studied by us rocks of early and middle Miocene age crop out at several localities on some of the structurally highest parts of the Ocala uplift as well as on its flanks. Near Linden in Sumter County is a thin patch of phosphatic clay and sand, probably of the Haw thorn formation, overlying fossiliferous (table 2) Tampa limestone (loc. 100). The Tampa is thin and rests on silicified Ocala limestone in this area. Silicified Tampa fossils (table 2) were found (loc. 69) by K. B. Ketner in clayey sand about 7 miles west of Dade City, at an elevation of about 110 feet. Large Miocene corals that occur near the base of the Hawthorn or the top of the Tampa were found (loc. 61) in clayey sand 5 miles southwest of Dade City at an eleva tion of over 200 feet. Ketner (oral communication, 1955) has traced the Tampa and Hawthorn formations, with but few interruptions, from the land-pebble phosphate district northward through the Dade City area to the Ocala uplift and the hardrock phosphate district in Hernando County.
That the Tampa and Hawthorn formations are now missing in large areas on the Ocala uplift is not denied, but the evidence indicates that there was extensive, if not complete, inundation of the uplift by lower and middle Miocene seas. The distribution of phosphate in the Tampa and Hawthorn formations has little areal relation to the crest of the Ocala uplift, because phosphate is found in the Hawthorn formation from South Carolina to southern Florida.
FAULTING
Previous to Vernon's (1951) work in Citrus and Levy Counties, Tertiary faulting had not been recognized in peninsular Florida. .We were able to prove the existence of a structural break, probably a fault, in northern Polk County (pis. 1 and'3).
The strike of this displacement is about N. 40° W. with the up- thrown side to the northeast. This structure appears to affect rocks up through the Suwannee limestone markedly, and even the Tampa and Hawthorn formations seem to be slightly displaced in some areas. Projected to the northwest the fault alines very well with faults shown by Vernon (1951, pi. 2) in Sumter and Citrus Counties. It also follows closely the major subsurface ridge which Vernon shows in Polk County on the top of his Inglis member of the Moodys Branch formation as used by him (the lower part of the Ocala lime stone of this report). Vernon shows the zero contour of the top of his Inglis displaced about 40 miles to the southeast by this fault zone;
60 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
the present work indicates this displacement may extend more than 50 miles. To the east of the fault line hi Polk County the Suwannee limestone, according to well logs, is missing, and Miocene rocks rest upon the Ocala limestone.
Locality 72 near Rock Ridge in northwestern Polk County lies near the projection of this fault. Chert boulders containing well- preserved fossils were found in a drainage ditch at this locality. The boulders were not hi place but were probably dug from limestone immediately below. The chert contained the following fossils identi fied by F. S. MacNeil: Turritella sp. aff. T. perduensis Mansfield, Cardium sp., Chione sp. cf. C. perduensis Mansfield, Turritella marlinensis Dall var.? and (or) T. carinata palmerae Bowles, and Periarchus lyelli Cooke subsp.?. The first 3 fossils probably indicate the Suwannee limestone. T. carinata palmerae is a species of Clai- borne (Avon Park limestone) age, and Periarchus lyelli has been reported only from the lower part of the Ocala limestone (Inglis member of Vernon, 1951, of the Moodys Branch formation).
In order to clarify the structure in the Rock Ridge area, 2 holes were drilled with a power auger; one (M9) about 1.5 miles east of and the other (MlO) about 1.5 miles south of locality 72. Both the holes and the exposure at locality 72 were at about the same elevation, about 90 feet. In the hole to the east fossiliferous limestone of the Ocala was found within 10 feet of the surface; it was overlain by clayey sand, probably of the Hawthorn formation. The hole to the south passed through about 15 feet of clayey sand and clay, probably the Hawthorn formation, and was bottomed after passing through about 5 feet of clay, sand, and fresh-water limestone, of the Tampa. The limestone contained the land snail Helisoma. Thus, the stratig raphy in this area indicates a fault with a displacement of 100 feet or more. The combination of Eocene and Oligocene fossils at locality 72 can be accounted for by material reworked into the Suwannee limestone.
Fossiliferous phosphatic limestone of the Tampa was found farther south in holes G90 and G91 (pi. 2) just east of the fault near Winter Haven, and to the north in Sumter County at locality 100 (pi. 2). Well logs in central Polk County show that the Suwannee limestone is 50-100 feet thick on the west side of the fault, but absent on the east side.
CONTACT BETWEEN THE TAMPA LIMESTONE AND THE HAWTHORNFORMATION
Subsurface features of the base of the Hawthorn formation and the thickness of the Tampa limestone are shown on plate 3. The map is chiefly of the surface of the Tampa limestone; however, in some areas to the east and north of Polk City the Hawthorn lies upon
GEOLOGIC HISTORY ^ 61
Eocene rocks. The information is based on outcrops of the formations, holes drilled during the course of this work, and well logs supplied by the Florida Geological Survey. It should be kept in mind that in many of these wells the base of the Hawthorn formation has been picked by us and does not necessarily coincide with the base as placed by the Florida Geological Survey.
North of about lat. 28° there is little correspondence between the structural contours on the base of the Hawthorn and the isopachs of the Tampa limestone. Highs and lows on the top of the Tampa limestone do not match thick and thin portions of the formation. Unfortunately not enough information was available to permit structure contouring of the top of the Suwannee limestone, the erosional surface of which affects the thickness of the Tampa. How ever, the irregularity of the base of the Hawthorn alone is submitted as evidence of some erosion of the Tampa limestone.
An approximate strike of the Tampa limestone was determined from the top of a fairly persistent unit of green sandy, dolomitic clay (see p. 25), which was noted in several wells in Polk County. The strike of the top of these beds, presumably a conformable surface within the Tampa, varied from west to N. 48° W. depending upon which combination of wells was used. The most persistent component was about N. 50° W. This strike gives a dip for the Tampa limestone of 8-10 feet per mile to the southwest, which is also the direction of greatest thickening of the formation. No reliable information on the attitude of the Hawthorn formation could be obtained because of a lack of traceable beds. Local dips are meaningless because of de formation caused by solution and slumping. However, it is evident (pis. 1 and 3) that the boundary of the Hawthorn formation in northern Hillsborough and Polk Counties trends approximately N. 60° E. across rising topography. Thus, a strike in this area of about N. 30° W. is indicated, with a dip to the west-southwest. If correct, these attitudes indicate a slight regional disconforinity between the two formations in this area.
No exposures that show clearly the details of the contact were found, but a contact, believed to be uncbnformable, between weathered Tampa and Hawthorn sediments is present at localities 6 and 24 (figs. 14 and 15), previously discussed. The presence of chert at the Tampa- Hawthorn contact and the possibility that the rock collected at locality 73 (see p. 31) represents reworked Tampa limestone are also suggested as evidence for an unconformity.
The fauna of the Tampa limestone (table 2) indicates, for some areas at least, a very shallow marine and, locally, a fresh-water environment of deposition, suggesting that only minor uplift or
601224 69 6
62 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
recession of the sea would have been necessary to initiate erosion of the formation.
The clay and silt fraction of two samples from the Davison well, one from the top of the Tampa and the other from near the base of the Hawthorn, were X-rayed 5 to determine whether there are any mineralogic changes across the contact. Quartz, orthoclase, mont- morillonite, and illite were found in the Hawthorn sample; quartz, plagioclase, montmorillonite, and attapulgite were found in the Tampa sample. This change in mineralogy reflects a change in depositional environment or a shift in source area.
STRUCTURAL FEATURES OF MIOCENE ROCKS
Figures 2, 13, and 15 and plate 3 show some of the structural features, both large and small, present in western Polk, northeastern Hillsborough, and eastern Pasco Counties.
: The larger structural features consist of hills and ridges which rise gently above the surrounding level terrain and which are underlain by orange iron-stained clay and sand. One area of such topographic highs extends from near Thonotosassa southward to the Alafia River. A small group of very low hills lies around the town of Knights north of Plant City; the higher hills in eastern Pasco County and the Lakeland ridge are similar features on a larger scale.
All of the hills and ridges mentioned appear to be underlain by orange sand and clay of the Tampa, Hawthorn, and undifferentiated Miocene and Pliocene rocks. The thin layer of Quaternary sand at the surface usually shows no such iron staining and is unconformable upon the older beds (fig. 13). Logs of drill holes show that the iron-stained zone follows the topography rather closely.
In most cases where subsurface data are available the formations rise under the topographic highs; the hills are due to thicker Miocene and Pliocene sediments localized over highs on the surface of the Suwannee or Tampa limestones. On plate 3 note the closed contours, hills and basins east and northeast of Tampa, and the continuity of the structural high across the upper Hillsborough River. This high matches well the present Lakeland ridge and Dade City high lands.
These hills are apparently part of the belt of Miocene clay and sand, which lies around the flanks of the Ocala uplift. In this area the belt has been breached by the Hillsborough and Withlacoochee River systems.
In detail, the persistence of some of these remnants of clay and sand may be due to their originally lower carbonate content, and resultant higher resistance to weathering and erosion. Possibly this
'Informal analyses by R. O. Petersen, U.S. Geological Survey. r
,: GEOLOGIC HISTORY 63
original deficiency of carbonate can be explained by the site of dep osition. As pointed out by Trask (1932, p. 93, 125) fine material and carbonate tend to be more abundant in deposits of submarine basins, whereas coarser material and less carbonate are deposited on submarine ridges and hills. The submarine topography (irregularities in the surface of the Tampa limestone) in Hawthorn time could have caused deposition of fine material and carbonate in the valleys, and coarser material with less carbonate upon the hilltops and ridges.
Some of the relief, particularly in the area northeast of Tampa, probably is due to solution depressions and sinkholes. Drill hole G7 (fig. 16) shows that very deep sinkholes exist in this area. SinalK scale faulting may also be responsible for some of the features. Vernon (1951, pi. 2) shows a structural high on his Inglis member of the Moodys Branch formation as used by him (lower part of the Ocala limestone of this report) which approximates the location of the Lakeland ridge.
Two good exposures, localities 6 and 13, show some of the minor structural features and details of distortion in this area (figs. 13 and 15). This minor deformation is due to solution of limestone and slumping of the overlying beds. '
SEDIMENTATION !SUWANNEE UMESTONE
The Suwannee limestone represents a period similar to that of the Ocala limestone, during which conditions promoted deposition of a pure limestone with only traces of very well sorted clastic material. Marine mollusks and Foraminifera flourished in the sea during the deposition of the Suwannee and their remains locally comprise a large part of the formation.
The lower part of the Suwannee limestone in the Davison well (see p. 10) is somewhat anomalous to the rest of the formation, but it is not known whether the lithology represented there is a result of a local or regional variation in deposition.
A quiet marine environment in warm waters of shallow to moderate depth is indicated for the Suwannee limestone.
TAMPA LIMESTONE
The beginning of the Miocene brought a distinct change in sedi mentation, both in environment and source area. Throughout the Eocene and Oligocene very little sand and clay i had been supplied to the sediments. In west-central Florida the beginning of deposition of the Tampa, however, is marked by beds of calcareous or dolomitic clayey sand and clay which accumulated locally in the: western Pclk County and Tampa areas. At the same time, and apparently: throughout the early Miocene, islands, estuaries, and fresh-water
501£24r 5fl 8
64 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
lakes became prevalent. From the fossil-distribution chart (table 2) it may be seen that the Tampa contains land and fresh-water, fauna at "several localities, which range from the base to near the top.of the formation. These localities also show a wide areal distribution, but most of them are in the vicinity of Tampa and the gulf coast.;
The clay mineral, attapulgite, found in parts of the Tampa lime stone may indicate a specific type of depositional environment. According to Millet (1952, p. 110, 113), "attapulgites apparently are found only in special environments of the basic lake series." The association of attapulgite with illite and with land and fresh water .fauna and montmorillonite clays in the Tampa therefore suggests a nearshore lagoonal or estuarine environment alternating with or associated with basic lakes. The latter were not necessarily undergoing dessication, however. This conclusion agrees well with the faunal characteristics of the formation.
Thus, the environment of the Tampa limestone was one of varied and shifting conditions. T^he water was shallow; islands and lagoons were common and persisted until nearly the end of Tampa deposition. Increased activity of ocean currents and the irregularity of the sea floor were probably responsible for transfer and localization of clastic materials. Pure limestone accumulated in local areas of fresh-water lakes. Probably minor weathering and erosion of the formation occurred in some areas while deposition was proceeding in others. As a result of these conditions the time-stratigraphic sequence of the Tampa is complex.
HAWTHORN FORMATION
Conditions which prevailed during most of early Miocene deposition began to change toward the close of Tampa time, and by Hawthorn time insular and lagoonal environments had given way to a more open marine setting as the sea transgressed.
The fauna of the Hawthorn formation consists almos.t entirely of mollusks, which prefer moderately shallow water but avoid stagnant brackish conditions. Such an environment would require a free circulation of water over a broad, relatively flat and stable sea bottom. Once established, these conditions must have remained stable for a long tune, and they seem to have been especially conducive to the deposition of phosphate.
The source of the phosphorus in the waters of the seas of late Tampa and Hawthorn times is a question that cannot be conclusively answered at present, but we favor the theory of Kazakov (1937; summarized in McKelvey and others, 1953, p. 55) in which-chemical precipitation of phosphate is brought about by the upwelling of cold currents from deep ocean basins over a shelving platform such as
GEOLOGIC HISTORY . ; 65
the Florida peninsula. This hypothesis limits the precipitation* of phosphate to-a depth of water between about 150 and 650 feet;
SAND AND CLAY OF THE J MIOCENE
The petrographic data obtained in this study show clearly that the sediments of Miocene age contain much more sand and clay and silt than the rocks of Eocene and Oligocene age, and that the sand is coarser than that deposited previously. The sudden influx of these clastic materials in Miocene sediments, particularly limestone, of peninsular-Florida is a problem because of the great distance to an obvious source of supply.
Some of the sand in the Miocene rocks of west-central Florida was doubtless derived locally from weathering and erosion of older rocks, and through weathering and reworking a gradual concentration of coarser particles was effected. This is suggested by the relatively consistent increase in grain size in beds .of younger age from the Suwannee through the Hawthorn. That a few sand grains as large as those found in later formations exist in the older rocks is shown by the fifth percentile values.
Extra-local sources for most of the clastic material are indicated, however, by other evidence. For example, sand reworked froin formation to formation should show better and better sorting if no new material were added. The data suggest that ,this is not the case, although sorting in all samples is very good. Furthermore, if a win nowing process occurred to remove more fine material for each succeeding formation, then the percentage of clay and silt should decrease with younger age, other conditions remaining constant. The opposite appears to be true (figs. 7, 8, 9, and table 4).
Berry (1916, p. 46) thought that the increase in supply of terrestrial material represented in northern Florida by the sedimentation of the Alum Bluff group .was probably due to an inland rise of land. The only obvious, means of transferring large quantities of sand into the Florida peninsular area during the Miocene, however, was through coastal,, movement of sand by longshore currents. This migration of sand would require a fairly continuous coastline or delta system extending some 400 miles from the site of deposition to source areas near the Piedmont of central Georgia and Alabama. The increase in the amount of garnet, staurolite, and other heavy minerals with the beginning of Miocene sedimentation tends to support this theory. This condition could have occurred in the early Miocene according to the paleogeog- raphy of Tampa time (Cooke, 1945, p. 112), but by mid-Hawthorn time such "land bridges" may have been inundated, cutting off the central,peninsula from further supply of terrigenous material. r
66 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
ever, no such impoverishment of clastic material is indicated .by the lithology of the Hawthorn formation. . : v ,-
The problem remains unsolved > but we point out that increase in clay and silt in the Miocene could be partly explained by a change in weathering.conditions and the possibility of addition of clay-forming minerals by ash falls from distant volcanic activity. ' Grim (1933, p. 358) noted that in the fuller's earth deposits of the Superior Earth Co., Ocala, Fla., "many of the fragments of isotropic material, which have a maximum diameter of 0.12 mm, have a cellular structure suggesting that they are organic remains; others strongly resemble bubble and shard remnants of volcanic glass." Bramlette (written communication, 1953) stated that "the high content of montmorillo- nite and attapulgite could perhaps be explained, however, as the alteration product of the relatively coarse fraction only of vitric pyroclastics that might,thus have accumulated along with the quartz sand that is an important constituent of the Hawthorn dolomite." Numerous beds of pure waxy green attapulgite-montmorillonite clay and clayey limestones were found by us in the Miocene rocks of west-central Florida.
SUMMARY OF GEOLOGIC HISTORY
The mid-Tertiary geologic history of this area may be summarized as follows: The Suwannee limestone was laid down in warm quiet waters over the eroded surface of the Ocala limestone. "Coarse" sandy limestone was deposited locally on this surface as the sea ad vanced and fragments of Eocene rocks were locally reworked into the base of the Suwannee. In eastern Polk County the Suwannee was thin and probably wedged out against the higher parts of this area. Near the close of the Oligocene, perhaps before deposition was com pleted in some areas, gentle arching and minor faulting occurred along the axis of the Ocala uplift, bringing Oligocene and Eocene rocks adjacent to one another in some places. Erosion cut gentle valleys in the Suwannee limestone, and removed most of the Suwannee that was present in the northeast half of Polk County.
In Tampa tune the sea advanced over the erosion surface on rocks of Oligocene and Eocene age, deposition beginning in some places with Beds of clayey sand and clay. The deposits thinned to the north and east but overlapped the Eocene-Oligocene contacts, and in some places probably spread beyond the limits of Oligocene deposition. Islands, lagoons, and fresh-water lakes followed the shifting shoreline. The greatest extent of the shallow Tampa sea covered most, if not all, of western peninsular Florida. Toward the end of ; Tampa 1 time the island-lagoon environment began to give way to a more regular shore line as the sea retreated. Probably at the close of Tampa tune re-
.:.:.::.. ECONOMIC-GEOLOGY : .. ; . @7
newed movement occurred on the fault in Polk County, and erosion locally removed some of the thin Tampa sediments from the east side of the fault in northern Polk County. . , ' :,.':'
In Hawthorn tune the sea then advanced over a slightly irregular surface depositing calcareous sand and clay near the shore and on the higher parts of the sea floor, and limestone elsewhere. As marine transgression continued the Hawthorn sediments overlapped rocks from early;Miocene to middle Eocene in age and a broad, relatively open seaway was developed in Polk and Hillsbprough Counties. The Hawthorn accumulated slowly and conditions favorable to the deposi tion of phosphate persisted over a wide area for a long time. There may have been additions to the Miocene sedimentation by volcanic ash falls. Only minor adjustments in the structure occurred after the Hawthorn was deposited.
ECONOMIC GEOLOGY
PHOSPHATE AND URANIUM
Near-surface deposits of secondary phosphates containing concent trations of uranium are present around the northwest fringe of the land-pebble phosphate district in a narrow, discontinuous belt, which begins near the Alafia River northeast of Riverview and curves north eastward north of Plant City. Most of the uranium and phosphate deposits in this fringe area lie in the belt mapped (pi. 1) as sand unit and phosphorite unit of the Hawthorn formation. Radiometric logs of core holes in this belt show (figs. 2, 3, and 16) in places two zones or peaks bf abnormal radioactivity. The upper zone, where present, is in the unit designated as undifferentiated sand and clay of Miocene and Pliocene age. The lower zone, not as well developed, usually is found at the top of the Tampa limestone. .. '..
At locality 44 and other places north and west of Plant City vesic ular white sandstone, probably a leached portion of the Hawthorn formation, contains abundant aluminum phosphate. A raw grab sample of this rock from locality 44 contained 0.008 percent equivalent uranium.6 Some of the deposits of secondary phosphate, particularly in the lower zone, are associated with chert fragments. , . .
Locally, where the two radioactive zones mentioned above are superimposed by weathering and downward migration of uranium, relatively high concentrations of uranium may exist within 10 or 15 feet of the surface. The aforementioned belt should be prospected if it becomes feasible to utilize deposits of uranium of the leached-zone type which have thin overburden and are not underlain by economic phosphate deposits.
Two zones of phosphate and uranium are found also in the Dade Laboratory No. 115958.
68 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
City highland area an upper zone near the base of the Hawthorn formation, arid a lower zone near the base of the Tampa limestone. The upper zone, which is similar to the vesicular white sandstone of the aluminum phosphate zone in the land-pebble phosphate district, is 10-15 feet thick--in drill h^les G112 and Gil3 (fig. 3), and lies about 100 feet above sea level./ The lower zone, which consists of-lenses of rnassive white slightly uraniferous phosphate, chiefly colloidal apatite similar to the "hardrock" phosphate found farther north, is 5-10 feet thick in holes G110-G113, and ranges from 80 to 50 feet above sea level. One exposure, locality 64, of this "hardrock" type phosphate was found southwest of Bade City at an elevation of about 120 feet. A raw grab sample of this rock was 70 percent soluble in hydrochloric acid, and contained 26.9 percent P205 , 37.3 percent CaO> but only 1.9 percent A1203 . 7 The uranium content was negligible.
The, limestone of the, Tampa and Hawthorn formations v,contains only sparse phosphate nodules and traces of uranium, except in the land-pebble district where a concentration has been effected by weathering of the Hawthorn formation.
For further evaluation of the uranium and phosphate resources of this area the reader is referred to Cathcart and McGreevy (1959).
LIMESTONE AND DOLOMITE
Analyses suggest that there are, in the land-pebble phosphate district, deposits of dolomite as high grade as those now mined in Manatee and: Sarasota Counties. The possibility of recovering some of the bedrock as a byproduct of phosphate mining deserves further investigation.
Every sample of limestone of the Hawthorn analyzed contained at least 9 percent MgO. Many of the samples are bedrock from the bottoms of phosphate pits. The average MgO content of 16 grab samples of limestone of the Hawthorn from phosphate mines was 15.8 percent. These mines include Sydney (loc. 39), Eleanor (loc. 41), Saddle Creek (loc. 74), Pauway (loc. 75), Achan (loc. 76), Noralyh (loc. 78), Clear Springs (loc. 79), Varn (loc. 80), Watson (loc. 81), and Peace Valley (loc. 82), and an old pit (loc. 77) near Bartow.8 Samples from Sydney, Watson, and Peace Valley mines contained an average of 17.5, 19.9, and 17.5 percent MgO respec tively. Composite samples of rock mined at 2 dolomite quarries in Manatee and Sarasota Counties contained 17.3 and 18.5 percent MgO.9 : -.
T Laboratory No. 115969» Laboratory Nos.: loc. 39, 115952-115954; loc. 41, 115955, 115956; loc. 74, 115974; loc. 75, 115976; loc. 76,
115977; loc. 78,115980; loc. 79,115982; loc. 80,115983; loc. 81,115984; loc. 82,115985,115986; loc.77,115978,115979. « Laboratory Nos.: 115993, 115994.
LITERATURE CITED - 69
There are no deposits of limestone of present economic value in the area mapped. Limestone of the Hawthorn is too thickly covered and generally too impure. The Tampa limestone contains some pure limestone beds, but these zones are discontinuous and thin. The Suwannee is a relatively pure limestone but in this area it con tains considerable chert.
LITERATURE CITED
Alien, J. H., 1846, Some facts respecting the geology of Tampa Bay, Florida:Am. Jour. Sci., 2d ser., v. 1, p. 38-42.
Altschuler, Z. S., and Cisney, E. A., 1952, X-ray evidence of the nature of thecarbonate-apatites [abs.]: Geol. Soc. America Bull., v. 63, no. 12, pt. 2,p. 1230.
Applin, P. L., and Applin, E. R., 1944, Regional subsurface stratigraphy andstructure of Florida and southern Georgia: Am. Assoc. Petroleum GeologistsBull., v. 28, no. 12, p, 1673-1753.
Bergendahl, M. H., 1956, Stratigraphy of parts of DeSoto and Hardee Counties,Florida: U.S. Geol. Survey Bull. 1030-B.
Berry, E. W., 1916, The physical conditions and age indicated by the flora of theAlum Bluff formation: U.S. Geol. Survey Prof. Paper 98-E, p. 41-59.
Brown, R. W., 1934, Celliforma spirifer, the fossil larval chambers of miningbees: Washington Acad. Sci. Jour., v. 24, no. 12, p. 532-539.
1935, Further notes on fossil larval chambers of mining bees: WashingtonAcad. Sci. Jour., v. 25, no. 12, p. 526-528.
CathcarVJ. B., and McGreevy, L. J.y 1959, Results of geologic exploration bycore drilling, 1953, land-pebble phosphate district, Florida: U.S. Geol.Survey Bull. 1046-K.
Cathcart, J. B., Blade, L. V., Davidson, D. F., and Ketner, K. B., 1953, Thegeology of the Florida land-pebble phosphate deposits: Intern at. Geol.Cong., 19th, Algiers 1952, Comptes rendus, sec. 11, pt. 11, p. 77-91.
Colbert, E. H., 1932, Aphelops from the Hawthorn formation of Florida:, Florida Geol. Survey Bull. 10, p. 55-58.
Cole, W. S., 1941,. Stratigraphic and paleontologic studies of wells in Florida:Florida Geol. Survey Bull. 19.
Cooke, C. W., 1915, The age of the Ocala limestone:!U.S. Geol. Survey Prof.Paper 95-1, p. 107-117.
-1931, Seven .coastal. terraces in the Southeastern States: Washington Acad. Sci. Jour., v. 21, no. 21, p. 503-513.
1943, Geology of the coastal plain of Georgia: U.S. Geol. Survey Bull. 941.
1945, Geology of Florida: Florida Geol. Survey Bull. 29.Cooke, C. W., and Mansfield, W. C., 1936, Suwannee limestone of Florida [abs.]:
Geol. Soc. America Proc. 1935, p. 71-72. Cooke, C. W., and Mossom, Stuart, 1929, Geology of Florida: Florida Geol.
Survey AnnrRept. 20, p. 29-227. Cushman, J. A., 1920, Lower Miocene Foraminifera of Florida! U.S. Geol.
. Survey Prof. Paper 128-B, p. 67-74. Cushman, J. A., and Ponton, G. M., 1932, The Foraminifera of the upper, middle,
and part of the lower Miocene of Florida: Florida Geol. Survey Bull. 9.
70 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
Ball, W. H., 1890-1903, Contributions to the Tertiary fauna of Florida, with a special reference to the Miocene silex beds of Tampa and the Pliocene beds of the Caloosahatchie River: Wagner Free Inst. Sci. Trans., v. 3, pts. 1-6.
1915, A monograph of the molluscan fauna of the Orthaulax pugnax zone of the Oligocene of Tampa, Florida: U.S. Nat. Mus. Bull. 90. :
Dall, W. H., and Harris, G. D., 1892, Correlation papers; Neocene: U.S. Geol. Survey Bull. 84.
Fischer, A. G., 1949, Petrology of Eocene limestones in and around the Citrus- Levy County area, Florida: Florida Geol. Survey Kept. Inv., no. 9, p. 41-70.
Gardner, Julia A., 1926-50, The molluscan fauna of the Alum Bluff group of Florida: U.S. Geol. Survey Prof. Paper 142, pts. 1-9.
Grim, R. E., 1933, Petrography of the fuller's earth deposits, Olmstead, Illinois, with a brief study of some non-Illinois earths: Econ. Geology, v. 28, no. 4, p. 358.
Grim, R. E., Dietz, R. S., and Bradley, W. F., 1949, Clay mineral composition of some sediments from the Pacific Ocean off the California coast and the Gulf of California: Geol. Soc. America Bull., v. 60, p. 1785-1808.
Heath, R. C., and Smith, P. C., 1954, Ground-water resources of Pinellas County, Florida: Florida Geol. Survey Rept. Inv., no. 12.
Heilprin, Angelo, 1887, Explorations on the west coast of Florida and in the Okeechobee wilderness: Wagner Free Inst. Sci. Trans., v. 1.
Hopkins, R. H., 1942, The dolomitic limestones of Florida: Florida Geol. Survey Rept. Inv., no. 3.
Johnson, L. C., 1888, The structure of Florida: Am. Jour. Sci., 3rd ser., v. 36, p. 230-236.
Kazakov, A. V., 1937, The phosphorite facies and the genesis of phosphorites, in Himmelfarb, B. M., and others, eds., Geological investigations of agri cultural ores USSR: [U.S.S.R.] Sci. Inst. Fertilizers and Insecto-Fun- gicides Trans., no. 142, Leningrad, p. 95-113. (Translation published for the 17th sess. Internat. Geol. Cong.)
Kerr, P. F., 1937, Attapulgus clay: Am. Mineralogist, v. 22, p. 534-550.Ketner, K. B., and McGreevy, L. J., 1959, Stratigraphy of the area between
Hernando and Hardee Counties, Florida: U.S. Geol. Survey Bull. 1074-C.:Leith, C. K., 1925, Silicification of erosion surfaces: Econ. Geology, v. 20, no. 6,
p. 513-523.MacNeil, F. S., 1944, Oligocene stratigraphy of southeastern United States: Am.
Assoc. Petroleum Geologists Bull., v. 28, no. 9, p. 1313-1354. 1946, The Tertiary formations of Alabama: Southeastern Geol. Soc.
Guidebook 4th Field Trip, p. 55. 1947, Correlation chart for the outcropping Tertiary formations of the
eastern Gulf region: U.S. Geol. Survey Oil and Gas Inv. Prelim. Chart 29. 1949, Pleistocene shorelines in Florida and Georgia: U.S. Geol. Survey
Prof. Paper 221-F, p. 95-106. Mansfield, W. C., 1937, Mollusks of the Tampa and Suwannee limestones of
Florida: Florida Geol. Survey Bull. 15. Matson, G. C., 1915, The phosphate deposits of Florida: U.S. Geol. Survey Bull.
604. Matson, G. C., and Clapp, F. G., 1909, A preliminary report on the geology of
Florida, with special reference to the stratigraphy: Florida Geol. SurveyAnn. Rept. 2, p. 25-173.
.... v LITERATURE CITED i -71
Matson, G. C., and Sanford, Samuel, 1913, Geology and ground waters of Florida: U.S. Geol. Survey Water-Supply Paper 319. . : !
McKelvey, V. K, Swanson, R. W., and Sheldon, R. P;, 1953, The Permian phosphorite deposits of western United States: Internat. Geol. Gong., i'Qth, Algiers 1952,; Comptes rendus, sec. 11, pt. 11, p. 46-64. ; ! : .
Millot, Georges, 1952, Prospecting for useful clays in relation with their condi tions of genesis, in Problems of clay and laterite genesis symposium: New York, Am. Inst. Mining Metall. Engineers, p. .107-114. . : '
Mossom, D. S., 1925, A preliminary report on the limestones and marls of Florida: Florida Geoli Survey Ann. Rept. 16, p. 27, 203. :
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Puri, H. S., 1953a, Zonation of the Ocala group in peninsular Florida, [abs.]: Jour. Sed. Petrology, v. 23, p. 130.
l953b, Contribution to the study of the Miocene of the Florida pan handle: Florida Geol. Survey Bull. 36. : :
Sellards, E. H., 1915, The pebble phosphates of Florida: Florida Geol. Survey Ann. Rept. 7, p. 25-116. . '.
1916, Fossil vertebrates from Florida; a new Miocene fauna; new Pliocene species; the Pleistocene fauna: Florida Geol. Survey Ann. Rept. 8, p. 77-119.
Simpson, G. G., 1930, Tertiary land mammals of Florida: Am. Mus.: Nat. His tory Bull., v. 59, art. 3, p. 149-211.
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1933, Glossary and correlation charts of North American Tertiary mam mal-bearing formations: Am. Mus. Nat. History Bull., v. 57, p. 91.
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Vaughan, T. W., and Cooke, C. W., 1914, Correlation of the Hawthorn forma tion: Washington Acad. Sci. Jour., v. 4, no. 10, p. 250-253.
Vernon, R. O., 1951, Geology of Citrus and Levy Counties, Florida: Florida Geol. Survey Bull. 33. .
Wentworth, C. K., 1922, A scale of grade and class terms for clastic sediments: Jour. Geology, v. 30, p. 377-392. :
Wetmore, Alexander, 1943, Fossil birds from the Tertiary deposits of Florida: New England Zool. Club Proc., v. 22, p. 59-68.
White, T. E., 1942, The lower Miocene mammal fauna of Florida: Harvard Coll. Mus. Corhp. Zoology Bull., v. 92, no. 1.
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E.
Sta
te H
ighw
ay 3
9 to
Cry
stal
.S
prin
gs t
own;
tur
n w
est
for
0.35
m
ile,
then
no
rth
on
dirt
roa
d; e
xpos
ure
in s
mal
l di
tch
on w
est
side
of
road
.L
ocal
ity
56:
Sta
te
Hig
hway
39
, 0.
8 m
ile n
orth
of C
ryst
al
Spri
ngs
tow
n; s
hallo
w b
or
row
pit
s ea
st s
ide
of r
oad.
Loc
alit
y 57
: S
tate
H
ighw
ay
39,
1.4
mile
s no
rth
of C
ryst
al
Spri
ngs
tow
n; s
hallo
w b
or
row
pi
t 10
0 yd
s w
est
of
road
. -
Loc
alit
y 58
: S
tock
w
ater
ing
pit
on p
riva
te l
and,
abo
ut
0.8
mile
wes
t an
d so
uth
of
loca
lity
57.
Sta
te H
ighw
ay 5
4, a
bout
5.5
m
iles
wes
t of
Z
ephy
rhill
s,
at n
orth
sid
e of
bri
dge
over
N
ew,R
iver
; fr
agm
ents
dug
fr
om c
reek
.F
rom
L
acoo
chee
tu
rn
sout
h on
pa
ved
stre
et o
ver
rail
ro
ad t
rack
s, c
onti
nue
sout
h on
mai
n di
rt r
oad
for
abou
t 1
mile
unt
il r
oad
para
llel
s tr
acks
on
the
east
; p
it o
n pr
ivat
e la
nd a
bout
0..2
mile
w
est
of r
oad.
Sta
te H
ighw
ay 5
2 fr
om D
ade
City
, ab
out
2.4
mile
s w
est
of
Pas
co
in
very
sh
allo
w
road
cut
near
co
rral
s on
_ so
uth
side
of r
oad;
als
o sp
oil
bank
s of
di
tch
abou
t 0.
3 m
ile n
orth
of
road
cut.
Che
rt a
nd t
ripo
li,
cave
rnou
s,
iron
-sta
ined
, br
own,
re
d,
whi
te,
cobb
les.
Che
rt,
brow
n,
gray
, bl
ack,
lo
cally
pyr
itic
, fo
ssili
fero
us,
trip
oli;
si
licif
ied
cora
ls
as
soci
ated
wit
h gr
ay
to
red
clay
ey s
and.
Che
rt,
gray
, an
d tr
ipol
i; c
hert
co
ntai
ns
abun
dant
min
ute
quar
tz s
pher
ulit
es.
Lim
esto
ne,
soft
, w
hite
, gr
anu
la
r,
slig
htly
san
dy,
irre
gu
larl
y fo
ssili
ferp
us;
uppe
r par
t th
in b
edde
d in
pla
ces
and
cont
ains
man
y ve
rtic
al
"pip
es"
wit
h gr
een
clay
.
San
d,
clay
ey,
dark
-bro
wn
to
gray
, ha
rdpa
n;
cont
ains
br
own,
or
ange
, an
d w
hite
sp
arse
ly
foss
ilife
rous
ch
ert
and
trip
oli;
als
o (a
t di
tch
to
nort
h),
ligh
t-ta
n ha
rd c
rys
ta
llin
e, v
ery
slig
htly
san
dy" "
f os
Bili
fero
us l
imes
tone
. - -
-
30
Pro
babl
y Su
wan
hee
alth
ough
so
me
cher
t re
sidu
al f
rom
the
T
ampa
li
mes
tone
pr
obab
ly
occu
rs i
n th
e ar
ea.
Cla
yey
sand
and
cor
als;
som
e of
the
cher
t m
ay b
e M
ioce
ne^
Loc
alit
ies
list
ed
here
ar
e on
ly a
few
of
man
y in
the
C
ryst
al
Spri
ngs
area
w
here
ch
ert
occu
rs.
Age
un
cert
ain,
b
ut
prob
ably
re
plac
emen
t of
O
ligoc
ene
rock
s.
Coo
ke (
1945
, p.
98)
.
74 MIDDLE TERTIARY ROCKS IN-PART OP WEST-CENTRAL FLORIDA
Thickne (feet)
1*1 "^l
HIIs-g§g|
«
I*.It
a a
li
^ °'§!.S a al* %! orfllil* |5
o
w o B«.
W 0co cO
LIST ?OF /EXPOSURES
QJ ^Q .U W
I2&1fe 0> ^a 0>
S3
-f-vrf
«*III<D ? 5*-1
Iff
43 g£
^"SJb^Slr*-t
Oc v
^ o .O 0}P5a
H K i-O aH gon 5w ~s-a a Ifc I
!'.H IS-g.,
o> *} o o O
oCO
I >O
I CO
bo a 8 £
Hi. ^r«2; feia J4 w ifllillllli
.3 13
i «5 a-»»
O oO e3 S e3
^^ * -*rHfjq.
v* r.W M
x iS
002
PQ ,02
Loc
ality
and
No.
(pi
. 2)
Acc
ess
Gen
eral
lith
olog
yT
hick
ness
(f
eet)
Rem
arks
TA
MP
A L
IME
ST
ON
E C
onti
nu
ed
Hil
lsb
orou
gh C
oun
ty C
onti
nu
ed
6. T
empl
e T
erra
ce
unde
rpas
s; N
SW
K s
ec.
19, T
. 28
S,
, R
. 20
E.
8. B
lack
wat
er C
reek
; N
W>i
sec
. 18
, T
. 2
18
., R
,22
E,
11.
40th
Str
eet
Bri
dge;
N
WK
sec.
33,
T.
28 S
., R
. 19
E.
12.
How
ard
Ave
. di
tch.
._
18.
Mor
ris
Bri
dge;
sec.
33,
T.
27 S
., R
. 20
E.
19.
Kin
g si
nkho
le;
sec.
18,
T.
28 S
., R
. 20
E.
U.S
. H
ighw
ay 3
01 a
bout
2.7
m
iles
nort
h of
junc
tion
wit
h U
.S.
Hig
hway
92;
roa
dcut
.
Sta
te H
ighw
ay 3
9 ab
out
8.5
mile
s no
rth
of P
lant
Cit
y;
spoi
l ba
nks
of .d
itch
.
40th
St.,
nor
thea
st o
f T
ampa
at
sou
th e
nd o
f br
idge
ove
r H
ills
boro
ugh
Riv
er;
smal
l bo
rrow
, pi
t, w
est
side
of
40
th
St.
-In
bloc
k be
twee
n H
owar
d A
ve.,
Col
umbu
s D
r.,
Arm
e
nia
Ave
., an
d K
athl
een
St.,
. T
ampa
, -
Mor
ris
Bri
dge
Rd.
, 0.
3 m
ile
nort
heas
t of
Mor
ris
Bri
dge
over
Hil
lsbo
roug
h R
iver
, or
ab
out
7 m
iles
nort
h of
junc
ti
on o
f M
orri
s B
ridg
e R
d.
and
old
U.S
. H
ighw
ay 3
01;
ditc
h be
side
roa
d.F
rom
in
ters
ecti
on
of
Fow
ler
Ave
. and
Mor
ris.
Bri
dge
Rd.
no
rthe
ast
of
Tam
pa,
turn
Sand
, cl
ayey
to
very
cla
yey,
an
d sa
ndy
ligh
t-gr
ay
to
gray
-gre
en i
ron-
stai
ned
clay
; ch
ert
and
trip
oli.
Lim
esto
ne,
whi
te,
slig
htly
sa
ndy,
gra
nula
r, lo
cally
sili
c-
ifie
d.
Lim
esto
ne,
whi
te
to
ligh
t-
brow
n,
slig
htly
sa
ndy
to
sand
y; t
hin
seam
s of
sili
ca.
Lim
esto
ne,
ligh
t-ta
n to
whi
te,
very
cla
yey,
san
dy;
patc
hes
and
lens
es
of
blue
-gre
en
sand
y cl
ay.
Lim
esto
ne, w
hite
, san
dy, p
art
ly
si
licif
ied,
fo
ssili
fero
us,
and
vari
colo
red
cher
t.
Lim
esto
ne,
ligh
t-ta
n,
hard
, sl
ight
ly s
andy
, fr
agm
enta
l, sp
arse
ly
foss
ilife
rous
; se
c-
12.0
6.5 1.5
9.0
See
fi
g.
15.
Silic
ifie
d lo
wer
M
ioce
ne
foss
ils
and
Side
r-
astr
aea
cora
ls.
Che
rt
is
prob
ably
silic
ifie
d fr
esh-
wat
er
limes
tone
, co
ntai
ning
Cha
ro-
phyt
e oo
goni
a.M
ansf
ield
(1
937^
p.
51
) ar
id
Coo
ke (
1945
, p.
127
) re
port
Su
wan
nee
- T
ampa
co
ntac
t he
re;
foss
ils o
f bo
th f
orm
a
tion
s pr
esen
t.
Now
ina
cces
sibl
e.
Not
in
pl
ace,
bu
t pr
obab
ly
from
dra
inag
e di
tch.
en 3 i I
20.
Tem
ple
Ter
race
;SW
% s
ec.
13,
T.
28 S
-., R
. 19
E.
21.
Cow
Hou
se C
reek
;S
E^ s
ec.
12,
T.
28
S.,
R.
19 E
. .
.
24.
Lam
our
pit
;se
c. 3
3, T
. 28
S.,
R.
19 E
.
25.
Har
ney
rail
road
cut;
S
WK
sec
. 26
, T
. 28
S.,
R.
19 E
.
26.
Hil
lsbo
roug
h R
iver
da
m;
NW
% s
ec.
29,
T.
28 S
., R
. 19
E.
sout
h fo
r 0.
5 m
ile,
turn
eas
t on
d
irt
road
fo
r 0.
4 m
ile;
si
nkho
le
200
feet
nort
h
of
road
.F
owle
r A
ve.,
nort
hea
st
of
Tam
pa,
at 0
.3 m
ile w
est
of
Hil
lsbo
roug
h R
iver
tu
rn
sout
h on
dir
t ro
ad f
or a
bout
0.5
mile
, ba
nk w
est
of r
oad.
Mor
ris
Bri
dge
Rd.
at
br
idge
ov
er
Cow
H
ouse
C
reek
, 0.
03
mile
nort
h
of
Fow
ler
Ave
.50
th
St.
an
d R
oble
s (E
ast
Slig
h)
Ave
., nort
hea
st
Tam
pa;
depr
essi
on,
nort
h
east
cor
ner
of s
and
pit
.
Rob
les
(Eas
t Sl
igh)
A
ve.,
nort
h
of
viad
uct
over
ra
il
road
tr
acks
ju
st
sout
h of
H
arne
y; r
ailr
oad
cut.
Turn
no
rth
fro
m E
ast
Hil
ls-
boro
ugh
Ave
. (U
.S.
Hig
h
way
92
) on
30
th
St.
pas
t T
ampa
wat
erw
orks
to e
nd
of r
oad;
out
crop
bel
ow d
am,
sout
h si
de o
f ri
ver.
onda
ry
carb
onat
e fr
actu
re
fill
ing.
Lim
esto
ne,
whi
te t
o li
ght-
tan,
sl
ight
ly
sand
y to
sa
ndy,
ha
rd,
frag
men
tal,
sec
onda
ry
carb
onat
e fr
actu
re
fill
ing;
sp
arse
gr
een
clay
ba
lls,
sp
arse
ly f
ossi
life
rous
; ov
er
lain
by
res
idua
l ch
ert
and
cl
ay.
Che
rt a
nd s
ilici
fied
lim
esto
ne,
gray
, w
hite
, br
own,
m
as
sive
, ba
nded
, li
my
pock
ets
in p
lace
s.L
imes
tone
, w
hite
to
lig
ht-
tan,
soft
, cl
ayey
, sa
ndy;
ov
er
lain
by
cl
ay,
sand
, an
d
cher
t,
the
last
co
ntai
ning
lo
wer
Mio
cene
fos
sils
.L
imes
tone
, w
hite
to
ligh
t-ta
n,
sand
y,
and
thin
se
ams
of
sand
y bl
ue-g
reen
cla
y gr
ad
ing
upw
ard
into
whi
te h
ard
very
sl
ight
ly
sand
y li
me
st
one;
at
to
p
is
light-
tan
slig
htly
sa
ndy
frag
men
tal
lim
esto
ne
that
w
eath
ers
sphe
roid
ally
. ;
San
d,
whi
te
to
gray
-gre
en,
and
ligh
t-ta
n so
ft
sand
y,
clay
ey l
imes
tone
.
5.0
5.0
8.0
8.0
An
addi
tion
al 3
.0 f
eet
of l
ime
st
one
is
expo
sed
in a
smal
l si
nk
on
east
si
de
of
road
ab
out
200'y
ards
east
-no
rth
ea
st o
f m
ain
outc
rop.
S
ilic
i
fied
co
ral
Side
rast
raea
si
li-
cens
is p
rese
nt i
n up
per
par
t of
out
crop
.P
ossi
bly
sili
cifi
ed
Suw
anne
e li
mes
tone
.
Lim
esto
ne
and
low
er
par
t of
se
ctio
n m
ay
be
cove
red
by
slum
p; e
xcel
lent
exa
mpl
e of
w
eath
erin
g; s
ee f
igur
e 14
.
On
east
sid
e of
cut
is r
ed-b
row
n cl
ayey
san
d, m
ostl
y re
sidu
al
from
Tam
pa
lim
esto
ne,
bu
t th
e up
per
0.5
feet
m
ay
be
Haw
thor
n fo
rmat
ion.
See
figu
re
10.
Bes
t ex
posu
re
of T
ampa
lim
esto
ne f
ound
in
wes
t-ce
ntra
l F
lori
da,
and
th
e on
ly
one
whe
re
orig
inal
ly
nonc
alca
reou
s . b
eds
of
the
form
atio
n ar
e w
ell
expo
sed.
U
sual
ly u
nder
wat
er i
n su
m
mer
and
fal
l. *
00
00
Loc
ality
and
No.
(pi
. 2)
Acc
ess
Gen
eral
lith
olog
yT
hick
ness
(f
eet)
Rem
arks
..
.
TA
MP
A L
IME
STO
NE
Con
tinu
ed
Hill
sbor
ough
Cou
nty-
^-C
ontin
ned
27.
Hil
lsbo
roug
h R
iver
; SE
% s
ec.
30,
T.
28 S
., R
. 19
E.
28.
No
rth
si
de
of
Hil
ls-
boro
ugh
Riv
er
dam
; S]
4 se
c. 2
0,
T.
28 S
., R
. 19
E.
29.
Sti
nky C
reek
; E>
£ se
c. 2
6, T
. 28
S.,
R.
18 E
.
31.
Con
e sa
ndpit
; N
W#
sec.
3,
T.
29 S
., R
. 19
E.
32.
Mac
Dil
l di
tch;
SW
%
sec.
26,
T.
30 S
., R
. 18
E.
Abo
ut 0
.2 m
ile
nort
h o
f S
ligh
A
ve.
near
end
of
18th
St.
, nort
hea
st T
amp
a; b
ould
ers
at e
dge
of H
ills
boro
ugh
Riv
er
about
100
yard
s n
ort
h o
f co
ncre
te
brid
ge o
ver
smal
l tr
ibu
tary
cre
ek.
Eas
t W
ater
s A
ve.
in n
ort
hea
st
Tam
pa,
about
1.3
mil
es e
ast
of
Neb
rask
a A
ve.
turn
so
uth
on d
irt
road
to d
am.
Nort
h
Blv
d.,
Tam
pa,
0.
55
mil
e nort
h o
f S
ligh
Ave
., or
0.
45
mil
e so
uth
of W
ater
s A
ve.;
in s
mal
l cr
eek
bott
om
ea
st a
nd w
est
of b
ridg
e.A
t 52
d S
t.,
nort
hea
st o
f T
am
pa,
turn
nort
h f
rom
Har
ney
Ave
. (F
ort
Kin
g H
ighw
ay)
at
Ora
nge
Hil
l ce
met
ery;
la
rge
san
dp
it;
lim
esto
ne e
x
pose
d in
de
epes
t par
t of
w
est
pit
.In
sou
thea
st p
art
of M
acD
ill
U.S
. A
ir F
orce
Bas
e, a
bout
0.7
mil
e nort
h a
nd 0
.3 m
ile
east
of
Qua
rant
ine
stat
ion
at
Gad
sden
P
oin
t;
spoi
l ba
nks
of c
anal
at
wes
t en
d of
gol
f co
urse
.
Che
rt,
gray
, si
licif
ied,
an
d
sand
y fo
ssil
ifer
ous
lim
e
ston
e.
Lim
esto
ne,
whi
te,
sand
y, f
rag-
m
enta
l, f
ossi
life
rous
, lo
call
y si
licif
ied.
Lim
esto
ne,
ligh
t-gr
ay t
o li
ght-
ye
llow
, sa
ndy,
har
d, f
ossi
li
fero
us;
abundan
t se
ams
of
seco
ndar
y ca
rbon
ate;
"fr
es
co"
wea
ther
ing.
Lim
esto
ne,
whi
te,
slig
htly
sa
ndy,
ha
rd,
silic
ifie
d,
fps-
si
life
rous
.
Lim
esto
ne,
whi
te,
slig
htly
sa
ndy,
ver
y fo
ssil
ifer
ous.
2.0
3.5
2.0
Apt
to b
e un
der
wat
er i
n ra
iny
seas
on.
Lim
esto
ne
expo
sed
here
is
si
mil
ar
to
uppe
r un
its
at
loca
lity
26
acro
ss r
iver
.
Wel
l-pr
eser
ved
silic
ifie
d sh
ells
w
eath
ered
put
of
lim
esto
ne
coul
d be
co
llec
ted
here
in
19
53.
.
Mos
t so
uthe
rly
expo
sure
of
T
ampa
lim
esto
ne k
now
n.
33.
Bea
ch P
ark:
NE
K
sec.
29,
T.
29 S
., R
. 18
E.
34.
Gra
y R
d.;
EK
sec
. 18
, T
. 29
S.,
R.
18
.K.
43.
Eu
rek
a
Sp
rin
gs:
N
Wtf
SE
tfse
c. 3
1,
T.
28 S
., R
. 20
E.
49.
Tam
pa
Wat
erw
orks
; E
& s
ec.
29,
T.
28
S.,
R.
19 E
.
Tur
n ea
st f
rom
W
est
Shor
e B
lvd.
at
Woo
dmer
e A
ye.
in
Bea
ch
Par
k;
in
ditc
h be
tw
een
divi
ded
stre
et.
Acr
oss
from
482
1 G
ray
Rd.
, ab
out
0.2
mile
wes
t of
Wes
t...
. Sh
ore
Blv
d.,.
Tam
pa.._
. .
U.S
. H
ighw
ay 9
2, t
urn
nort
h at
0.6
mile
wes
t of
int
erse
c
tion
of
U
.S.
Hig
hway
92
an
d F
aulk
enbu
rg R
d., o
r 0.8
m
ile e
ast
of j
unct
ion
of U
.S.
Hig
hway
s 30
1 an
d 92
; sc
at
tere
d bo
ulde
rs a
roun
d fi
sh
pond
s.30
th
St.,
nort
heas
t T
ampa
, ab
out
1.3
mile
s no
rth
of
Hil
lsbo
roug
h A
ve.
(U.S
. H
ighw
ay 9
2);
cons
truc
tion
ex
cava
tion
.
Lim
esto
ne,
whi
te t
o ta
n, v
ery
slig
htly
san
dy,
soft
, fo
ssili
-fe
rous
, ab
unda
nt s
econ
dary
carb
onat
e.
Lim
esto
ne,
ligh
t-ta
n,
very
slig
htly
san
dy,
very
fos
sili-
..
fer.o
us,
cobb
les;
.ove
rlai
n.by
..ir
regu
larl
y fo
ssili
fero
us g
ray
cher
t. L
imes
tone
, w
hite
, sl
ight
lysa
ndy,
fr
agm
enta
l, sp
arse
mic
rofo
ssils
.
At
base
: lim
esto
ne,
sand
y,
clay
ey,
soft
, ro
tten
, w
hite
to
lig
ht t
an,
wit
h le
nses
and
po
cket
s of
whi
te f
ine-
grai
ned
sand
; co
ntac
ts
irre
gula
r;
over
lain
by
sand
and
whi
te
to
gree
n,
spar
sely
fo
ssil
if
erou
s sa
ndy
clay
, re
sidu
al
from
lim
esto
ne.
8.5
Pro
babl
y in
pla
ce,
but
may
be
cont
amin
ated
by
fill.
...........
No
long
er a
cces
sibl
e.
Pas
eo C
ount
y
54.
Cab
bag
e S
wam
p;
NE
K s
ec.
22,
T.
26
S.,
R.
19 E
.
64.
St.
Leo
bo
rrow
pi
t;
sec.
6,
T.
25
Den
ham
-Wes
ley
Cha
pel
Rd.
(S
tate
Hig
hway
209
) ab
out
4.8
mile
s so
uthw
est
of W
es-
ley
Cha
pel;
sha
llow
bor
row
pi
t, w
est
side
of
road
.S
tate
Hig
hway
52,
abo
ut 1
.0
mile
eas
t of
St.
Leo
or
abou
t 2.
5 m
iles
sout
hwes
t of
Dad
e C
ity;
sh
allo
w
borr
ow
pit,
...JQ
U.th
sid
e_pf
ro
ad..
._..
..
Lim
esto
ne,
whi
te t
o gr
ay,
im
pure
, ha
rd,
sand
y,
abun
da
nt b
ands
of
br
own.
car
bo
nate
; co
bble
s..»
......
_...-.,
...
-. ...
Sand
, w
hite
to
br
own,
fi
ne
grai
ned,
ha
rd,
indu
rate
d,-
alum
inum
- p
hosp
hate
* "c
e-
men
t;
abun
dant
si
licif
ied
.. co
rals
in
rubb
le _
on s
urfa
ce..
Pro
babl
y T
ampa
li
mes
tone
; ap
t to
be
co
vere
d in
rai
ny
seas
on;
cora
l Si
dera
stra
ea
hill
sbor
oens
is
in
surf
ace
rubb
le".
Sim
ilar
in a
ppea
ranc
e to
som
e ha
rdro
ck p
hosp
hate
.
<£>
80 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
1§,3
l|S""'E-
Qeneral llthology
1
gj
5I13 o
[ESTONE Continued
>unty Continued
aTAMPA
Pasc
03 +$
8 ^
£H 2 'ft
, Si4
; .« § :C3 o. ' :
' O § * 3 O '
CQw ". :
"%' =*
PQ
mestone, white to light-gray, pure, hard, very fine grained, and white granular foraminiferal porous very slightly sandy limestone, licified pelecypods in clayey
sand.
h3 ; 02
4> <U bO _a |N- ' " ' .'"I
U3 +3 Q Q> *- 1 p< <^ f-i
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02 N : £<*
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oik County
0.
3S3
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fl \
03 *>
(-. -Po a<4-l 0
G cu
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03 "
w
imestone, light-tan to brown, hard, very slightly sandy to very sandy, sparse brown phosphate nodules; contains
fragments of rounded and angular pure very fine grained nonphosphatic non- fossiliferous limestone, and
abundant brown carbonate, locally very fossiliferous.
^
~«*i -u 43 i Q r< r- 'T3Owo>,r3.+jCj3 a & a ** o -*> 03^3 v o 3 m£ 3.lsia«i||T -t-> w jj rj r3McQo^-^3 ^^(N^S ra _ SO^ O5 *=> CO g ^
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PQ
oo
90.
Ph
illi
pp
ePar
kjN
W^
sec.
35
, T
. 28
S.
, R
. 16
E.
91.
Bay
yiew
; SW
%
sec.
16
, T
.29 S
., R
. 16
E
.
94.
Cry
stal
Bea
ch;
sec.
3,
T.
28 S
., R
. 15
E.
95.
Anc
lote
;_E
& s
ec.
1,
T.
27 S
., R
. 15
E.
Abo
ut 1
.5 m
ile n
orth
of S
afet
y H
arbo
r in
ban
k on
sho
re o
f T
ampa
Bay
, at
foo
t of
larg
e In
dian
mou
nd i
n P
hill
ippe
P
ark.
..
Fro
m t
he g
ulf
to B
ay B
lvd.
ea
st
of
Cle
arw
ater
, tu
rn
sout
h to
bay
abo
ut 0
.5 m
ile
wes
t of j
unct
ion
wit
h Sa
fety
H
arbo
r ro
ad;
outc
rop
on
beac
h.
U.S
. H
ighw
ay
19,
abou
t 1.
0 m
ile n
orth
of
Pal
m H
arbo
r tu
rn w
est
at C
ryst
al B
each
en
tran
ce;
turn
so
uth
2 bl
ocks
af
ter
cros
sing
ra
il
road
tr
acks
, an
d co
ntin
ue
to e
nd o
f ro
ad a
t be
ach.
Sta
te H
ighw
ay 1
5 (5
95)
abou
t-
0.5
mile
no
rth
of
Anc
lote
R
iver
at
T
arpo
n Sp
ring
s;
abou
t 20
0 fe
et n
orth
east
of
rail
road
cro
ssin
g in
sha
llow
di
tch
wes
t si
de o
f ro
ad.
tain
ing
abun
dant
pe
bble
s an
d su
bang
iila
r fr
agm
ents
of
cl
ay
like
that
be
low
; gr
ades
up
in
to
viol
et-b
lue
sand
y ve
ry's
ligh
tly
calc
are
ou
s cl
ay
cont
aini
ng
frag
m
ents
of
le
ache
d',
unfo
ssil-
if
erou
s li
mes
tone
. L
imes
tone
, w
hite
, cl
ayey
, ch
alky
, ve
ry s
ligh
tly
sand
y,
poss
ibly
dol
omit
ic.
Lim
esto
ne,
ligh
t-gr
ay,
brit
tle,
ha
rd,
sand
y,
dolo
mit
ic,
spar
sely
fos
silif
erou
s.
Lim
esto
ne, g
ray
to w
hite
, sof
t, sl
ight
ly
sand
y,
cong
lom
er
atic
, fo
ssili
fero
us,
and
gray
fo
ssili
fero
us
cher
t tr
ipol
i. ......
Lim
esto
ne,
ligh
t-ta
n,
very
sl
ight
ly
sand
y,
cong
lom
er
atic
, fo
ssili
fero
us.
58 bs
7; le a
r. 7, r, c, t, r- 3 y r-
.5
.. . .
.....
Acc
essi
ble
only
at
lo
w
tide
.R
ock
cont
ains
, in
ad
diti
on
to
low
er
Mio
cene
fo
ssils
, C
arol
ia,
'Per
iplo
ma,
an
d a
larg
e C
ardi
ta, :
;not
pre
viou
sly
repo
rted
fro
m T
ampa
lim
e
ston
e ;
may
be
ne
ar
or
at
cont
act,
wit
h H
awth
orn
for
m
atio
n.
Mos
t ac
cess
ible
at
low
tid
e.
Coo
ke,
1945
, p.
131
-132
.
00
Loc
ality
and
No.
(pi
. 2)
Acc
ess
Gen
eral
llth
olog
yT
hick
ness
(f
eet)
Rem
arks
TA
MP
A L
IME
ST
ON
E C
onti
nu
ed
Sum
ter
Cou
nty
" -
-
100.
L
inde
n; S
W%
sec
. 16
, T
. 22
S.,
R.
23 E
.S
tate
Hig
hway
50,
1 m
ile e
ast
of L
inde
n; s
hallo
w r
oadc
ut.
Lim
esto
ne,
whi
te,
slig
htly
. sa
ndy,
fos
silif
erou
s.0.5
The
ov
erly
ing
phos
phat
ic
sand
y cl
ay
may
be
m
iddl
e M
ioce
ne..-
HA
WT
HO
RN
FO
RM
AT
ION
. H
illsb
orou
gh C
ount
ya % » 1 CD
6. T
em
ple
T
err
ace
Und
erpa
ss;
NW
>£
SW
^sec
.19,
T.
28
S:,
R.2
0E
.9.
K
nigh
ts;
NE
>i s
ec.
6,
T.
28 S
., R
. 22
E.
10.
Riv
ervi
e\y;
WJ4
. sea
I-
"-
21, T
; 30
S.,
R.
20 E
.
13.
Man
go H
ills
cla
sec.
3,
T.
29 S
., R
. 20
E.
U.S
.. H
ighw
ay:
301,
.ab
out
2.7
mile
s no
rth
of ju
ncti
on w
ith
. U
.S.
Hig
hway
92
.; ro
adcu
t.
Sta
te
Hig
hway
39
, 0.
1 m
ile
nort
h of
in
ters
ecti
on
at
Kni
ghts
, 4
mile
s no
rth
of
Pla
nt .
.City
;, ra
ilro
ad .
cut,
east
sid
e.of
roa
d.
.'
.
U.S
. Hig
hway
301
, turn
sou
th
east
0. i
mil§
sou
th o
f so
uth
end
of
brid
ge
over
, A
lafi
a R
iver
," c
onti
nue
0,8
mile
to
arch
'bri
dge
over
sm
all c
reek
; ou
tcro
p ab
ove
and
belo
w
brid
ge i
n bo
ttom
of
ravi
ne.
Sta
te H
ighw
ay 5
79,
0.5
mile
no
rth
of ju
ncti
on w
ith
Sta
te
Hig
hway
57
4 at
M
ango
; la
rge
clay
pit
eas
t of
roa
d.
Sand
, cla
yey,
fin
e^ to
med
ium
j-
grai
ned,
gr
ay "
to
redd
ishr
"
Sand
, sl
ight
ly
clay
ey
to
clay
ey,
fine
- to
m
ediu
m-
grai
ned,
ta
n to
or
ange
- br
own;
,, co
ntai
ns
vesi
cula
r no
dule
s of
{sa
nd
cem
ente
d by
al
umin
um .
. pho
spha
te
and
hard
pah;
Lim
esto
ne,
ligh
t-ta
n to
'whi
te,
loca
lly
-4har
d,
irre
gu
larl
y
sand
y, a
nd:
very
cal
care
ous
ligh
t-ta
n to
whi
te s
ands
tone
; al
l con
tain
spa
rse
phos
phat
e no
dule
s.
" . .
Sand
, sli
ghtl
y cl
ayey
to c
laye
y,
fine
- to
m
ediu
m-g
rain
ed,
tan
to
redr
bro
wn
. int
er-
bedd
ed w
ith
slig
htly
san
dy
gray
-gre
en b
lock
y w
axy
clay
co
ntai
ning
spa
rse
plat
y fra
g-=
men
ts
Of
alum
inum
ph
os--
ph
ate
and
cher
t.
6.0
4.5 3. 5
20.
0
The
un
derl
ying
T
ampa
lim
e
ston
e is
al
so
expo
sed
here
A -
near
by
dril
l ho
le. .
.. .(M
l)
sho.
wed
that
at
leas
t 30
fee
t of
pho
spha
tic
sand
and
cla
y as
sign
ed
to
the
Haw
thor
n fo
rmat
ion
unde
rlie
the
sm
all
hill
at t
his"
loca
lity
.
Pro
babl
y th
e be
st p
erm
anen
t ex
posu
re o
f lim
esto
ne o
f th
e H
awth
orn
form
atio
n in
the
ar
ea.
Poss
ibly
pos
t-m
iddl
e M
ioce
ne.
Inte
rest
ing
min
or s
truc
tura
l fe
atur
es,
one
of
whi
ch
is
show
n in
fig
ure
13.
14.
Buc
khor
n S
prin
gs;
NW
# s
ec.
10,
T.
30 S
., R
. 20
E.
15.
Bel
l S
hoal
s;se
c. 2
4, T
. 30
S.,
. .,
R;:
20E
. ;
..,
16.
Ald
erm
an's
for
d;S
E#se
c.-1
8,
T.
;.
30 S
., R
.22
E.
22;
Buc
khor
n C
reek
; "
SW
^se
c.3
,T.
30 S
., R
. 20
E.
24>
Lam
our
pit
;se
c. 3
3, T
. 28
S.,
R.
19 E
.
25.
Har
ney
rai
lroa
d cu
t;
.....
S
W^s
ec.
26,
T.
28 S
., R
. 19
E.
Blo
omin
gdal
e R
d.,
turn
sou
th
on d
irt
road
abo
ut 2
.2 m
iles
ea
st o
f ju
nct
ion w
ith
U.S
. H
ighw
ay 3
01,
or a
bout
3.5
mil
es w
est
of B
loom
ingd
ale;
co
ntin
ue a
bo
ut
0.4
mil
e to
en
d of
roa
d at
spr
ing
pool
; lo
ose
boul
der
. dug
fr
om
spri
ng.
-.
'B
rand
on-B
oyet
te
Rd.
, so
uth
en
d of
-.B
ell.
Sho
als
brid
ge
over
Ala
fia
Riv
er,
about
6 m
iles
~ so
uth
of
B
rand
oh;
smal
l o
utc
rop
at
ri
ver'
s ed
ge.
Sta
te H
ighw
ay 3
9 (H
opew
ell-
P
inec
rest
R
d.)
about
5 m
iles
so
uth
of
Hop
ewel
l or
ab
out
1 m
ile
nort
h o
f P
ine-
cr
est
belo
w
brid
ge
over
A
lafi
a R
iver
.B
loom
ingd
ale
Rdl
ab
out
.2.4
m
iles
eas
t "o
f ju
ncti
on w
ith
U.S
. H
ighw
ay 3
01,
or a
bout
3.
2 m
iles
wes
t of
Blo
omin
g-
dale
; bo
rrow
pit
nort
h s
ide
of r
oad
at B
uckh
orn
Cre
ek.
50th
S
t. -a
nd J
Rob
les
(Eas
t S
ligh).
Ave.,
nort
heast
T
amp
a; n
ort
hea
st c
orne
r of
sa
ndpit
..R
oble
s (E
ast
Slig
h)
Ave
.; nort
h.o
f via
duct
ove
r ra
il
road
ju
st s
ou
th o
f H
arn
ey;
rail
road
^u
t.
---.-
-
Lim
esto
ne,
tan,
sand
y-
Lim
esto
ne, t
an, s
andy
, spa
rsel
y ph
bsph
atic
.
Lir
nest
pne,
tan
, sa
ndy,
pho
s-
phat
ic.
San
d,
ligh
t-gr
ay .
to
pfsi
nge-
br
pwn,
sli
ghtl
y cl
ayey
, fi
ne
grai
ned,
wit
h tr
ace
of v
ery
coar
se g
rain
s..
-
San
d,
clay
ey,
yell
ow-b
row
n;
cont
ains
spa
rse
cher
t fr
ag
men
ts.
-
'.
San
d,
oran
ge-b
row
n,
slig
htly
cl
ayey
, m
ediu
m-g
rain
ed;
trac
e of
coa
rse
grai
ns,
con-
-
tain
s-
spar
se
- che
rt--
fra
g
men
ts;
low
er co
nta
ct w
ith
Tam
pa
lim
esto
ne
grad
a-
tion
aL
.5 .5 5,5
2.5 .5
Acc
essi
ble
only
in
dry
seas
on.
, .
.-'
.'
Acc
essi
ble
only
in
dry
sea
son.
Pos
sibl
y po
st-m
iddl
e .M
ioce
ne.
Ove
rlie
s; r
esid
uum
of
T
ampa
'lim
esto
ne.
" .-
-..
00
CO
Loc
ality
and
No.
(pi
. 2)
Acc
ess
Gen
eral
lith
olog
yT
hick
ness
(f
eet)
Rem
arks
HA
WT
HO
RN
FO
RM
AT
ION
Con
tin
ued
H
illeb
orou
gh C
oun
ty C
onti
nu
ed .
00 s o o s I
31.
Con
e sa
ndpi
t; N
W.tf
se
c. 3
, T
. 29
S.,
R.
19 E
.
36.
Ala
fia
Riv
er;
SK
sec.
9,
T.
30 S
., R
. 20
E.
37*
Ala
fia
Riv
er ;
sec.
15,
T. 3
0 S.
, R
. 20
E.
38.
Ala
fia
Riv
er;
sec.
23,
T. 3
0 S.
, R
. 20
E.
39.
Syd
ney
min
es,
Am
er
ican
Cya
nam
id
Com
pany
; A
, B
, C
, D
, E
. see
s. 2
2,
34,
36,
T.
29
S.,
R.
21 E
.
41.
Ele
anor
m
ine;
SE
V£
sec.
29
,,T.
29
S.,
R.
22 E
.
At
52d
St.,
nor
thea
st o
f Tam
pa
, tu
rn n
orth
fro
m H
arne
y A
ve.
(For
t K
ing
Hig
hway
) at
O
rang
e H
ill
cem
eter
y;
larg
e sa
ndpi
t.B
y bo
at o
n A
lafi
a R
iver
; w
est
bank
of
ri
ver,
1.
0 m
ile
nort
heas
t of
Riv
ervi
ew.
By
boat
on
A
lafi
a R
iver
, ab
out
1.5
mile
s do
wns
trea
m
from
B
ell
Shoa
ls
brid
ge;
sout
h bi
ank
of ri
ver.
By
boat
on
Ala
fia
Riv
er, a
bout
1.
0 m
ile d
owns
trea
m f
rom
B
ell
Shoa
ls b
ridg
e; s
ever
al
outc
rops
, no
rth
bank
of
ri
ver.
:
Sta
te H
ighw
ay 6
0; n
orth
pit
s,
4.5
mile
s w
est
of j
unct
ion
of S
ta|e
Hig
hway
s 60
and
39
; so
uth
pits
, 1
mile
sou
th
of S
ydne
y w
ashe
r; e
ast p
its,
1
mile
sou
th o
f S
tate
Hig
h
way
6d
on
T
urke
y C
reek
ro
ad.
,"S
tate
Hig
hway
39
abou
t 0.
7 m
ile
sout
h of
Sta
te H
igh-
w
ay
60
at
Hop
e wel
l; ol
d w
aste
dum
ps e
ast
of r
oad.
Sand
, ve
ry
slig
htly
cl
ayey
^ m
ediu
m-
to c
oars
e-gr
aine
d,
whit
e,
tan
, dar
k-v
iole
t-
gray
; ov
erlie
s T
ampa
lim
e
ston
e; c
onta
ct g
rada
tion
al.
Lim
esto
ne,
whi
te
to
light
s gr
ay,
very
san
dy;
cont
ains
ph
osph
ate
nodu
les
and
lens
es o
f w
hite
ver
y sl
ight
ly
sandy
har
d f
ine-
gra
ined
lim
esto
ne.
Lim
esto
ne,
very
san
dy,
con
ta
ins
phos
phat
e no
dule
s.
Lim
esto
ne,
hard
, sa
ndy,
lig
ht-
tan
to
ligh
t-gr
ay,
clay
ev,
loca
lly
dolo
mit
ic,
spar
sely
, fo
ssil
ifero
us;
co
ntai
ns
abun
dant
ph
osph
ate
nod
ul
es a
nd p
hosp
hati
c de
men
t.L
imes
tone
, w
hite
to
lign
t-ta
n,
sand
y,
chal
ky,
dolo
mit
ic;
cont
ains
pho
spha
te n
odul
es.
Lim
esto
ne,
whi
te,
chal
ky,
dol
om
itic,
sli
ghtl
y sa
ndy;
con
ta
ins
phos
phat
e no
dule
s.
5.0 1.0
1.0
5.0
Pro
babl
y H
awth
orn
form
a*
tion
, bu
t 'm
ay b
e po
st-m
id
dle
Mio
cene
.
Mos
t ac
cess
ible
at
lo
w
tide
; pr
obab
ly v
ery
near
bas
e of
H
awth
orn
form
atio
n.
Bes
t ex
pose
d at
. lo
w
tide.
Bes
t ex
pose
d at
lo
w
tide
in
dr
y se
ason
; th
e la
rges
t kn
own
perm
anen
t ex
posu
re
of
limes
tone
of
" th
e H
aw
thor
n fo
rmat
ion
in
this
re
gion
.
Old
m
ine;
lo
ose
piec
es
of
limes
tone
may
be
foun
d on
du
mps
.a
42.
Boy
ette
min
e, A
mer
ica
n A
gric
ultu
ral
Che
mic
al C
orp.
;se
c. 1
5,
T.
31
S.,
R.
21 E
. 44
. Ic
hepa
kesa
ssa
ditc
h,ea
st;
sec.
2.
and
" T.
28 S
., R
. 22
E.
45.
Cam
pbel
l B
ranc
h;
NW
% s
ec.
18, T
. 28S
..R
.21E
.
50.
Val
rico
rail
road
cut
; S
WK
sec.
24,T
.29
S.,
R.
20 E
.
Sta
te
Hig
hway
39
, ab
out
4 m
iles
sout
h of
P
inec
rest
tu
rn w
est
abou
t 2.5
mile
s to
w
ashe
r;'
pits
to
so
uth
of
was
her.
--K
nigh
ts-G
riff
iri
Rd.
, ab
out
4 m
iles
east
of
Kni
ghts
abo
ve
and
belo
w
brid
ge
over
dr
aina
ge c
anal
.
Ant
ioch
Rd.
, 0.
4 m
ile n
orth
of
Pla
nt
Cit
y-T
hono
tosa
ssa
Rd.
, or
abo
ut 3
mile
s no
rth
of
U.S
. H
ighw
ay
92
via
Mcl
ntos
h an
d A
ntio
ch R
ds.;
smal
l out
crop
in c
reek
.S
tate
Hig
hway
60,
turn
nor
th
abo
ut.
1.3
m
iles
east
of
B
rand
on,
cros
s tr
acks
, tu
rn
wes
t fo
r ab
out
0.4
mile
; ra
ilro
ad c
ut.
Lim
esto
ne,
ligh
t, ye
llow
, cl
ayey
, ve
ry s
ligh
tly
sand
y,
dolo
miti
c, f
ossi
lifer
ous;
con
ta
ins
phos
phat
e no
dule
s.
Sand
, w
hite
to
lig
ht^g
ray,
cl
ayey
, fi
ne-
to
coar
se
grai
ned,
in
dura
ted,
. hi
ghly
ve
sicu
lar,
ce
men
ted
by..
alum
inum
pho
spha
te.
-. .
San
d,
clay
ey,
fine
- to
coa
rse
gr
aine
d, d
ark-
gray
to
dark
- re
d-br
own;
co
ntai
ns a
few
lu
mps
of
al
umin
um
phos
ph
ate
cem
ente
d sa
nd.
San
d,
very
sl
ight
ly
clay
ey,
fine
- to
coa
rse-
grai
ned,
fai
r
ly u
nifo
rm o
rang
e-br
own.
3.0 1.0
15.0
Bes
t ex
pose
d in
dr
y se
ason
; ou
tcro
p ex
tend
s fo
r a
mile
or
so
al
ong
ditc
h.
Exp
osed
onl
y in
dry
sea
son.
Pas
co C
ount
y
53.
Bor
row
pit
s ;se
c. 2
6, T
. 26
S.,
R.
21 E
.
60. P
asad
ena
rail
road
cut
; . N
E^
sec.
10,
T.
25
S.,
R.
21 E
.
Old
roa
d to
Cry
stal
Spr
ings
fr
om Z
ephy
rhill
s, a
bout
0.7
m
ile s
outh
of
U.S
. H
ighw
ay
301;
sh
allo
w p
its
wes
t si
de
of r
oad.
U.S
. H
ighw
ay 3
01;
1.5
mile
s so
uth
of
Bad
e C
ity
city
li
mit
s tu
rn w
est
on p
aved
ro
ad K
mile
to ra
ilroa
d cr
oss
in
g;
rail
road
cu
t so
uth
of
cros
sing
.
Cla
y,
sand
y,
mot
tled
re
d,
gray
, an
d br
own;
lo
ose
"chu
nks
of
silic
ifie
d co
rals
an
d ch
ert,
trip
oli.
Cla
y, v
ery
sand
y, l
ight
-bro
wn
to
oran
ge,
.sem
i-in
dura
ted
in
plac
es;
cont
ains
fr
ag
men
ts a
nd n
odul
es o
f alu
mi
nu
m.p
hosp
hate
and
sli
ghtl
y sa
ndy
gray
-gre
en c
lay.
2.0
15.0
Res
idua
of
T
ampa
li
mes
tone
groba
bly
.pre
sent
als
o; c
oral
id
eras
trae
a hi
llsbo
rens
is
as
loos
e ru
bble
.
Bot
h T
ampa
an
d H
awth
orn
form
atio
ns m
ay b
e pr
esen
t. Si
licif
ied
cora
ls,
Side
rast
raea
hi
llsbo
roen
sis,
fou
nd i
n pl
ace
near
bo
ttom
of
ex
posu
re
abou
t a
foot
abo
ve a
gre
en
clay
bed
.
00
MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
3 ^N
g
p2 .
If fl^^1
H
General lithology
. Access
fJla0£ aI03
§"3
|
FORMATION Continued
bounty Continued
Z e
HAWTHOI . Pas
><* & i* & : -
: ! o c3 2 H = :
. ; if * w aa' ° 3
3' ! i 2
i 03 *GO i ft OJ O>
' i ! a * s in o: '. c8 fc^-*3
« C-l r^H 02' ! \! £ §' ' ; i i s| -; ;* S
io ' ; us oIN ' ; i ci «3
!
Sioi'S-Hg !g-S '^fS'Sli & S g|l5°.:|.2 -y.-J.p-§..
SslJli^i^'^Slili-.g**j.3h:h ->ge-snl« -iri § : 81 J S" l**l -I &i!!^i'r-i-:riii;^3f2-pid^c«S ;>»w2 E? S-gS^ SP^&bi « ,§ « fl s 8>o s£J3'aJ,i<U enic3 w 75-.3rt >4aO A 7v"^aBafe-i^s -21 ^-^ &-^|!lllll.2 |?ll« . ' 08 OS
CQ ' . ;OQ 02
IflJlJEa^ :«i-* s.sx&o 5 'if 1^l^l|3 111^ |«sIS|lH^ ^a«S^ - : :l^!1^!!"^!^^ § a^-g^ws >,o,d >»-eio^£ ..Q 3 g « US g <n <s 0 |o c<i<S43
l^|:f^|41^ §|f°*fSfl!ef||*|l^«^lp»>-Hb.ti c'3S o ''::<-tSS-dO-tS.^io3OooWp«J3o4»p-pl'CisSfloS5'-iow43S-M 43 -*a .fn ;CQ CQ
j-T1" ^ ~ ^! !* ** cJ ^ ^ "O - : '&C* ^<(N
«Cr] '- iT
^ QJ (M ."tn -^H >x,-.^CdCQ ' n-t 00 *^ ""^CN <^ CM ^ ' * " rH ' dNfrv" "-^O -; i-ty ""^PH ^ CM C^ ("a el rvi ' 03 ^^ ^"^ . *"3 w K . a> o . -.«.
3 h^ ^ tn <1) /vJ * (U i^JO^tCQ '4s SW T3 w'W
» :: 3 &
r-i 00 --HCO CO t«
»olk County .." .
p^
O flj
CO.
SiiN" %
Q)rt;d
'^j
CQ .COa> .a>H -»-Ja 'A
Q.^ .' a & 2H-
o ' ;o> '
amestone, slightly sandy, slightly clayey, yellow, "soft,
fossiliferous; overlain .by sandy light-tan clay, con taining abundant phosphate nodules, and by clayey gray sand, with abundant thin i
)mbee;Rd. east of Lakeland; at about 3.8 miles north of U.S. Highway 92 turn east on Ritter Rd. to Coronet mine washer; turn south- southwest across railroad tracks to pits; section lo-
w0 '
oT-Sri"' 2 S ~ S g<wf4-ojo'*
1«IS 'c_| o CQ « '.-
. 8 TOOO o ®t>-
O O w« . <"00"r»
74 B
, C
, D
. S
addl
e C
reek
m
ine,
A
mer
ican
C
yana
mid
C
om
pan
y;
sees
. 14
and
23,
T.
28 S
., R
. 24
E
.
75.
Pau
way
min
e,A
mer
ican
Agr
i
cult
ural
Che
mic
al
Cor
p.;
sec.
32,
T.
28 S
., R
. 24
E.
cate
d on
ea
st
face
of
cu
t m
ined
in F
ebru
ary
1954
.
U.S
. H
ighw
ay
92
east
fr
om
Lak
elan
d; p
its
are
about
2 m
iles
ea
st
of
city
li
mit
s;
sect
ion
loca
ted
near
cen
ter
of s
ec.
14 a
bout
100
yard
s nort
h o
f ro
ad o
n w
est
face
of
cu
t m
ined
in
F
ebru
ary
1954
.
U.S
. H
ighw
ay
98,
sou
thea
st
of
Lak
elan
d; 0
.3 m
ile
east
of
Lak
e H
olli
ngsw
orth
tu
rn
sout
h fo
r 1.
3 m
iles
to m
ine
area
; se
ctio
n lo
cate
d ne
ar
cent
er
of
sec.
32
on
w
est
face
of
cut
min
ed i
n F
ebru
ar
y 19
54.
lens
es
of s
andy
ve
ry
ligh
t gr
eeni
sh-g
ray
clay
, co
ntai
n
ing
abundan
t so
ft
whi
te
ph
osp
hat
e no
dule
s.
Lim
esto
ne,
slig
htly
sa
ndy,
sl
ight
ly
clay
ey,
light-
tan,
soft
, sl
ight
ly
ph
osp
hat
ic;
over
lain
by
ve
ry
clay
ey,
sand
y li
mes
tone
con
tain
ing
abu
nd
ant
frag
men
ts
of
blue
-gra
y cl
ay,
and
ve
ry
coar
se
ph
osp
hat
e no
dule
s;
over
lain
by
sl
ight
ly
sand
y bl
ue-g
ray
clay
, w
ith
wax
y,
oliv
e-gr
een
patc
hes,
an
d
patc
hes
and
lens
es o
f .f
ine
gr
aine
d gr
ay s
and,
con
tain
in
g ab
undan
t fi
ne t
an p
hos
p
hat
e sa
nd;
uppe
r co
nta
ct
fair
ly
shar
p
and
ir
regu
lar.
Lim
esto
ne,
clay
ey,
very
sl
ight
ly
sand
y,
whi
te
to
bro
wn,
f oss
ilif
ero
us,
sp
arse
ly p
hosp
hati
c, l
ocal
ly
sili
cifi
ed
and
do
lom
itic
; ov
erla
in
by
slig
htly
sa
ndy
whi
te t
o l
ight
-gra
y sl
ight
ly
calc
areo
us
clay
, co
ntai
ning
ab
undan
t sa
nd-
to p
ebbl
e-
size
pho
spha
te;
over
lain
by
slig
htly
cl
ayey
li
ght-
gray
- gr
een
sand
, co
ntai
ning
pho
s
phat
e sa
nd
and
gran
ules
, an
d pa
tche
s of
so
ft
whi
te
phos
phat
ic c
lay;
upp
er c
on
tact
sha
rp.
5.0
13.
0
Haw
thor
n pr
obab
ly t
hin.
A
c
cess
ible
on
ly
in
acti
vely
m
ined
pit
s.
Mat
eria
l inc
lude
d as
Haw
thor
n Q
fo
rmat
ion
clea
rly
resi
dual
CP
fr
om
lim
esto
ne
at
po
int
£3
whe
re s
ecti
on w
as t
aken
. § oft 00
00 00
Loc
ality
and
No.
(pi
. 2)
Acc
ess
Gen
eral
lith
olog
yT
hick
ness
(f
eet)
Rem
arks
HA
WT
HO
RN
FO
RM
AT
ION
Con
tin
ued
P
olk
Cou
nty
Con
tin
ued
76 A
, B
. A
chan
min
e,
Inte
rnat
ional
M
iner
als
and
Che
mic
als
Cor
p.;
sees
. 23
and
26,
T.
30 S
., R
. 23
E.
77.
Pulp
pla
nt
pit
; S
W#
se
c. 6
, T
. 30
S.,
R.
25 E
.
78.
Nor
alyn
min
e, I
nte
r
nat
ion
al 'M
iner
als
and
Che
mic
als
Cor
p.;
sees
. 29
an
d 32
, T
. 30
S.,
R.
25 E
....
79.
Cle
ar S
prin
gs m
ine,
V
irgi
nia-
'Car
olin
a C
hem
ical
Cor
p.;
sec.
33,
T.
30 S
., R
. 25
E.
80.
Var
n m
ine,
.'Sw
ift
and
Co.
; se
c. 2
5,
T.
31 S
., R
. 25
E
., an
d se
c. 3
0, T
. 31
S.,
R.
26 E
.
Sta
te H
ighw
ay 3
7, s
outh
fro
m
Mul
berr
y .a
bout
3.
5 m
iles
; in
SW
}4 s
ec.
23 a
t. so
uth
end
of
cu
t m
ined
in
F
ebru
ary
1954
.
Sta
te H
ighw
ay 6
0; t
urn
nort
h
0.1
mil
e w
est
of B
arto
w c
ity
lim
its,
cr
oss
rail
road
an
d tu
rn
wes
t fo
r 0.
2 m
ile;
la
rge
pit
to
nort
h o
f ro
ad.
U.S
. H
ighw
ay
17 s
outh
fro
m
Bar
tow
; ab
out
2.0
mil
es
sout
h of
ci
ty
lim
its
turn
w
est f
or a
bout
0.4
mil
e; t
urn
so
uth
/for
about
1.0
mile
to
min
e ar
ea w
est
of r
oad.
Inte
rsec
tion
of
U.S
. H
ighw
ay
17 a
nd S
tate
Hig
hway
655
, 4
mil
es s
outh
of
Bar
tow
.
Sta
te H
ighw
ay 6
30,
east
fro
m
Fo
rt
Mea
de;
about
1 m
ile
east
of
Pea
ce
Riv
er w
here
ro
ad
turn
s so
uth,
tu
rn
nort
hea
st i
nto
min
e ar
ea.
Lim
esto
ne,
sand
y, s
oft,
ligh
t-
tan,
slig
htly
fo
ssil
ifer
ous,
do
lom
itic
; co
ntai
ns
spar
se
sand
- to
pe
bble
-siz
e ph
os
phat
e;
uppe
r co
ntac
t not
seen
.
Lim
esto
ne,
very
sl
ight
ly
sand
y, w
hite
, so
ft,
very
fos
si
life
rous
; co
ntai
ns
spar
se
phos
phat
e sa
nd
and
gr
an
ules
.L
imes
tone
, pu
re,
soft
, li
ght-
ye
llow
, sl
ight
ly f
ossi
life
rous
, do
lom
itic
, co
ntai
ns
spar
se
phos
phat
e sa
nd
and
gran
ul
es.
Lim
esto
ne,
very
sl
ight
ly
sand
y,
whi
te t
o li
ght-
gray
, fo
ssil
ifer
ous,
dol
omit
ic.
Lim
esto
ne,
slig
htly
sa
ndy,
sl
ight
ly c
laye
y, l
ight
-yel
low
, sp
arse
ly f
ossi
life
rous
, do
lo
mit
ic;
cont
ains
spa
rse
sand
- to
gra
nule
-siz
e ph
osph
ate.
3.0
4.0
Most
of
mat
eria
l ab
ove
lim
e
sto
ne
beli
eved
to
be y
oung
er
th'a
n H
awth
orn
form
atio
n;
up
per
su
rfac
e of
li
mes
tone
ex
pose
d at
n
ort
h
end
of
aban
done
d pit
bet
wee
n S
tate
H
ighw
ay
37
and
road
to
P
ierc
e in
W%
sec
. 26
.A
cces
sibl
e on
ly i
n dr
y se
ason
. O
ne o
f th
e be
st l
ocal
itie
s fo
r fo
ssil
s in
H
awth
orn
form
a
tion.
81.
Wat
son
min
e, S
wif
t an
d C
o.;
sees
. 8,
17
and
20,
T.
32
S.,
R.
25 E
.
82.
Pea
ce V
alle
y m
ine,
...
. ..I
nter
nati
onal
Min
eral
s an
d C
hem
ical
s C
orp.
; se
es.
8, 9
, an
d 17
, T
. 31
S.,
R.
25 E
.83
.' K
athl
een
rail
road
cut
; SW
>4 s
ec.
17,
T.
27"
" s:,
R. 2
3'E.
86.
Ora
nged
ale
(Fox
tow
n)bo
rrow
pit
;N
EJ4
SW
& S
ec.
8.
- -
T.
27
S;,
R.
24 E
-.--
U.S
. H
ighw
ay
17;
about
2 m
iles
sou
th o
f F
ort
Mea
de,
turn
wes
t to
"S
and
Mou
n
tain
" an
d W
atso
n w
ashe
r,
and
then
ce
sout
hwes
t to
m
ine
area
.O
ld b
lack
top
road
sou
th f
rom
to
wn.
of.
Hom
elan
d. a
bout
1.5
mil
es.
Sta
te H
ighw
ay 3
5A,t
o K
ath
- le
en,
turn
no
rthw
est
from
"t
own,
" cr
oss
rail
road
" tr
acks
, an
d tu
rn n
orth
wes
t ag
ain
to
end"
of
road
bes
ide
trac
ks;
' ra
ilro
ad c
ut.
Sta
te H
ighw
ay 3
3 no
rth
from
L
akel
and;
at
ab
out
1.0
mil
e fr
om
city
lim
its
keep
le
ft o
n ol
d P
olk
Cit
y ro
ad,
at a
bout
2.0
mil
es t
urn
eas
t an
d
foll
ow
pave
men
t fo
r ab
out
2 m
iles
mor
e ea
st a
nd
no
rth
; bo
rrow
pit
so
uth
side
of
road
.
Lim
esto
ne,
fair
ly p
ure,
li
ght-
ta
n
to
whi
te,
foss
iltf
erou
s,
dolo
mit
ic,
cont
ains
sp
arse
sa
nd-
to g
ranu
le-s
ize
phos
p
hat
e.
Lim
esto
ne,
clay
ey,
tan
to
whi
te,
slig
htly
fos
sili
ferp
us,
dolo
mit
ic.
Cla
y, s
ligh
tly
sand
y to
san
dy,
ligh
t-g
r a
y-g
r e
e n,
w
axy,
"blo
cky
"fra
ctur
e;
over
lain
by
ligh
t-gr
ay
to
yell
owni
ediu
m-g
r a
i n e
'd
slig
htly
cl
ayey
sa
nd,
wit
h a
- few
co
arse
gra
ins;
upp
er c
on
tact
sh
arp,
ir
regu
lar;
ov
erla
in
by s
ligh
tly
clay
ey t
o c
laye
y li
ght-
gray
, m
ediu
m-g
rai&
ed
sand
, tr
ace
of c
oars
e gr
ains
, co
ntai
ning
abundan
t oys
ters
an
d
pect
ens
com
pose
d" o
f so
ft t
ripo
li,
and
loca
l tr
aces
of
ph
osph
ate
nodu
les
or
vesi
cula
rity
; up
per
con
tact
gf
adat
iona
l wit
h up
per
Mio
ce
ne (?
) m
icac
eous
cl
ayey
sa
nd.
San
d,
clay
ey,
med
ium
- to
fi
ne-g
rain
ed,
ligh
t-gr
ay,
mo
ttle
d r
ed-b
row
n.
4.0 1.5
Typ
ical
ex
posu
re
of
mid
dle.
Mio
cene
cl
ay
and
sa
nd(f
ig. -
12).
----
-
KT a o GO GO GO
C
O
Loc
ality
and
No.
(pi
. 2)
.Acc
ess
Gen
eral
lith
olog
yT
hick
ness
(f
eet)
Rem
arks
HA
WT
HO
RN
FO
RM
AT
ION
Con
tinu
ed
Man
atee
Cou
nty
CO
O
96.
Tam
pa G
ap d
rain
; S
&se
c. 3
6, T
. 33
S.
, R
. 17
E.
97.
Roc
ky B
luff
; se
c. 9
or
16,
T.
34 S
., R
. 18
E.
98.
Sou
ther
n D
olom
ite
Co.
pit
: S
^sec
. 13
, T
. 34
S.,
R.
17 E
.
U.S
. H
ighw
ay 4
1 ab
out
1 m
ile
sout
h of
R
ubon
ia;
spoi
l ba
nks
of d
rain
age
ditc
h.
U.S
. Hig
hway
301
(S
tate
Hig
h
way
43
),
abou
t 1.
3 m
iles
nort
heas
t of
Ell
ento
n tu
rn:
sout
h th
roug
h w
oods
abo
ut
200
yard
s to
bea
ch.
Fro
m j
unct
ion
of U
.S.
Hig
h
way
s 41
and
301
at
Pal
met
to
turn
ea
st o
n U
.S.
301
for
abou
t 0.
7 m
ile t
o
sign
of
S
outh
ern
Dol
omit
e C
o.,
turn
sou
th a
bout
0.5
mile
to
pit
s.
Lim
esto
ne,
sand
y,
clay
ey,
whi
te,
soft
, sl
ight
ly f
ossi
li-
fero
us;
cont
ains
tr
ace
of
fine
pho
spha
te s
and.
Lim
esto
ne,
slig
htly
sa
ndj',
cl
ayey
, lig
ht-y
ello
w,
dolo
- m
itic
; co
ntai
ns s
pars
e ph
os
phat
e sa
nd.
Lim
esto
ne,
ligh
t-ta
n to
whi
te,
.ver
y sl
ight
ly
sand
y an
d cl
ayey
, do
lpm
itic,
. sof
t, co
n
tain
s tr
ace
of
phos
phat
e sa
nd.
....
1.0
6. 0
Mos
t ac
cess
ible
at
low
tid
e.
Sara
sqta
Cou
nty
99.
Flo
rida
Dol
omit
e C
o.
pit;
NJ^
sec.
6,
T.
36S
.,R
.18E
,
Sta
te H
ighw
ay 6
83,
0.9
mile
so
uthe
ast
of U
.S.
Air
For
ce
Bas
e no
rth
of
Sar
asot
a;
dolo
mit
e pi
ts.
Lim
esto
ne,,
slig
htly
cl
ayey
, li
ght-
gree
n-gr
ay,
mas
sive
, do
lom
itic
; tr
ace
of
very
fi
ne p
hosp
hate
san
d.
;4.:5:
Pro
babl
y ...
sam
e;
as
loca
lity
give
n by
C
ooke
(1
945,
p.
16
0).
Drill holes Gl-^-Gl? were> logged by Carr and *Alverson; holes G105-G114 were logged by Ki B. Ketner, and hole G115 was logged by R. Gi Petersen* The, latter logs were interpreted by us, however. The fonnational contacts were .picked primarily on the basis of lithology.
In the lithologic description, the primary constituent is given first, followed by modification, Contacts.between the units are grada- tional, unless otherwise specified. Terms denoting abundance of constituents, as used in these logs, are defined below.
Terms ' Percent Terms PercentTrace, very slightly.___.-_--- <1 Abundant..------____---_-.-_ 20-50Sparse, sparsely, slightly.-__:_. 1-10 Very...____1.________________ > 20No modifier........--__.__ 10-20 Very abundant...___-_____..-__ >50
Depth
From (ft In)
'To (ft in)
Lithology :
Gl, :. 17, T. 28 S...R. 22 E., Hillsborough County, Fla. Elevation, 120 feet
0 05 05 86 8
9 1
18 9
19 5 :22 7
22 11
25 2
26 3
32 10
34 2
5 05 86 89 1
18 9
19 5
25 2
26 3
32 10
34 2
37 3
Quaternary:.Not cored. ...'.' : No recovery, .' ; Sand, tan, medium-grained. . No recovery.
Undifferentiated Pliocene and Miocene:Sand, light-tan to gray, medium-grained, slightly clayey;
contains sparse lumps of sandstone 'cemented by aluminum phosphate.
Sand,. white, medium-grained, slightly clayey, inter- lehsing with light-green very slightly-sandy laminated
. clay. Middle Miocene, Hawthorn formation:
Clay, very slightly sandy, light-green to light-brown. Sand, light-gray, slightly clayey, interlensing with light-
green clay; both contain trace of phosphate nodules. Clay, light-green, .mottled light-red-brown to yellow-
brown, very slightly sandy at top, laminated. Clay, gray-green to yellow-green, slightly . sandy to
sandy, laminated; contains 5 percent silt-size black grains.
Clay, yellow-gray, very slightly sandy, -slightly calcare ous; lower contact sharp. , :
Sand, light-gray, medium-grained, calcareous;,containssparse amber sand-size phosphate.
: 'Sand, light-gray, fine- to medium-igrained; contains sparse amber sand-size ptiosphate,; and trace of silt- size black grains.
91
92 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
Depth
From (ft in)
To (ft in)
Llthology
Gl Continued
41 943 6
44 1
45 5
37 941 9
43 644 '1
44 5
45 11
Lower Miocene, Tampa limestone:No. recovery.Sand, gray-green, fine-grained, clayey, slightly calcare
ous at bottom; contains trace to sparse tan and amber sand-size phosphate rand cherfrfragments.
No recovery.'Clay, slightly sandy, sligntly calcareous; contains sparse
amber and gray sand-size phosphate.Limestone, very -slightly sandy, soft; contains abundant
hard fragments, and trace (?) of phosphate (?).Limestone, white to light-gray, slightly sandy and
clayey; contains fragments of rounded calcareous clay, and trace of phosphate (?).
G2, SWJ^NEM sec. 5, T. 28 S., R. 22 E., Hillsborough County, Fla. Elevation, 105 feet
0 05 0
7 1
7 4
7 4
12 1
14 7
15 2
17 11
21 8
Quaternary:Not cored. , ;_. . \ ,.-..;-.-- r .s.r j. . Sand; brown:'to? lighj^brpwn, slightly clayey, medium-
grained, JronistaiBed7'v ' " ^'"- No recovery.
Undifferentiated Pliocene and Miocene:Sand, tan to light-green-gray, slightly clayey to clayey,
medium- to fine-grained; contains thin lenses of light- green slightly sandy clay, and trace to sparse white sand-size phosphate; lower contact sharp.
Middle Miocene, Hawthorn formation:Clay, gray, mottled brown, slightly sandy; contains thin
lenses of gray to White slightly clayey sand containing trace of phosphate (?).
Sand, gray-green to gray, medium- to fine-grained,clayey; contains trace of white phosphate.
Lower Miocene, Tampa limestone:, Clay, gray-yellow.^ slightly-- sandy- tp/" sandy; i contains
chert'fragments-coated with tripoli or white phos phate; lower contact sharp.
Limestone, light-gray to light-tan, slightly iron-stained, clayey, slightly sandy, soft to hard at base, contains seams and fragments of green clay, abundant chert fragments, and trace of phosphate(?).
G3, NEJiSEJi sec. 31, T. 27 8., R. 22 E., Hillsborough County, Fla.Elevation, 100 feet ;
0 0
7 2
20 6
7 2.
20 6
22 0
Quaternary: No recovery. , ; .
Undifferentiated Pliocene and'Miocene: 'Sand, light-gray, medium- to fine-grained, very slightly
clayey, well-sorted;^"Sand, light-gray, fine-grained, clayey; contains abundant
fragments-of sandstone cemented by aluminum phos phate; lower contact sharp.
LITHOLOGIC LOGS OF CORE HOLES 93
Depth
From (ft to) -
To- (ft to)
Lithology ;
G3 Continued
22 0
29 6
31 4
32 6
41 4
48 6
52 5
58 9
67 7
69 10
74 6
76 678 6
29 6
31 4
32 6
37 7
41 4
48 . 6
52 5
58 9
67 7
69 10
74 6
76 6
78 679 6
81 0
Middle Miocene, Hawthorn formation:Clay, gray, mottled red-brown, very slightly sandy;
contains trace to sparse fine sand-size white phos phate; lower contact sharp.
Sand, very light gray, medium-grained, slightly clayey, slightly iron stained at top; contains fragments of sandstone cemented by aluminum . phosphate, and trace of white soft phosphate. |
Clay, gray, slightly sandy to sandy; contains', trace of white phosphate; lower contact sharp.
Sand, gray, slightly clayey to clayey, medium- to fine grained, locally iron-stained; contains sandstone frag ments, cemented by aluminum phosphate.
Clay, gray-green, silty (quartz), interlaminated with clayey silt, contains trace of white phosphate, and trace of silt-size heavy minerals (?).
Lower Miocene, Tampa limestone:Poor recovery; .probably, white medium-grained sand
with thin beds of yellow-brown very clayey sand.Clay, light-gray-green, iron-stained, slightly sandy to
sandy, laminated; contains. twiglike fragments of silica. . ; .
Sand, white, fine-grained, very slightly clayey; inter- lenses with green sandy clay; unit contains heavy minerals.
Poor recovery; probably a lens of white to red-brown fine-grained very slightly clayey sand, containing visible heavy minerals.
Poor recovery; probably white slightly clayey fine grained sand with thin lenses of gray, clayey sand containing hard white fragments with casts and molds of small .mollusks.
No recovery; probably the same as 67 ft. 7 in. to 69 ft. 10 in.
Sand, light-gray to tan, fine-grained, slightly clayey to clayey; contains thin layer of light-gray chert, and visible heavy minerals. :
No recovery; probably same as 74 ft. 6 in. to 76 ft. 6 :'in. . Limestone, white to light-tan, very slightly to slightly
sandy, clayey; interlenses with yellow-brown very calcareous, laminated clay.
Limestone, white, hard, very pure; contains casts and molds of mollusks, Helisoma sp.
G4, NWJiSEJi sec. 19, T. 27 8., R. 22 E., Hillsborough County, Fla. Elevation, 95 feet
0 0
5 0
5 0
19 4
Quaternary:Not .cored.
Undifferentiated Pliocene atod Miocene:Sand, light-gray .to tan, medium- to fine-grained, locally
iron-stained; contains trace to sparse white fine sand- size phosphate, small patches of' white aluminum phosphate, and trace of heavy minerals.
94 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
Depth
Fro(ft,*
m tin)
T(ft
o in)
Lithology
G4 Continued
19
23
2424
05
5
18
282829323438.41
50
57
0678
13
17
4
0
711
23
24
2426
00
4
5
36
101
1145
10
4
55
18
28
28293234384150
57
0007
: 6
1
6 T
813
17
18
0
7
1110
Middle Miocene, Hawthorn formation:. Clay, light-blue to gray-blue and violet, slightly sandy
to sandy; contains abundant irregular fragments ofsoft limestone, and patches of fine- to medium-grained quartz sand.
Lower Miocene, Tampa limestone:Clay, as in 19 ft. 4 in. to 23 ft. 0 in., but laminated;
contains trace of fine fragments of phosphatized(?)limestone, and fragments of brown chert.
Oligocene, Suwannee limestone:No recovery; possibly a chert layer.Limestone, white, hard, pure, porous; contains Phacoides
(Miltha), sp. aff. P. chipolanus Dall, Turritella n.sp.(?), Turritella sp. aff. T. bowenae Mansfield, andKuphus incrassatus (Gabb).
G5, SEJiSWJ* sec. 7, T. 27 S., R. 22 E., Hillsborough County, Fla.Elevation, 80 feet
04
5
3
610
11145
10
4
Quaternary:Not cored.Sand, dark-brown, medium-grained; lower contact
sharp.Sand, very light gray to tan, fine-grained, very slightly
to slightly clayey; intervals of no recovery.Sand, gray to light-gray, medium- to fine-grained,
slightly clayey to clayey.Clay, gray, trace of very fine sand.Sand, light-gray, medium-grained, slightly clayey.No recovery.Sand, white, fine-grained.Sand, dark-brown, fine-grained.No recovery.Sand, dark-brown, fine- to medium-grained, slightly
clayey; intervals of no recovery.Sand, gray, fine-grained, slightly clayey; intervals of
no recovery.No recovery, no advance; probably Suwannee chert.
G6, SEMNW& sec. 35, T. 28 S., R. 21 E., Hmsborough County, Fla.Elevation, 120 feet
0076
1"5'
Quaternary:Not cored, no recovery.Sand, red-brown, fine-grained, very slightly clayey.No recovery; probably sand. ;Sand, light to very dark brown, fine- to medium-grained;
contains black .organic material at base; lower contact sharp. . : -
Undifferentiated Pliocene and Miocene:Sand, light-gray to light-brown, fine-grained^ clayey,
locally iron-stained.No recovery.
LITHOLOGIC LOOS OF CORE HOLES 95
Depth
From (ft In)
To (ft In)
Lithology
G 6 Continued
22 .4
23. 2
24 9
32 942. 1
44 10
48. ,4
55 3
57 11
60 5
67 7
75 4
22 4
23 2
24 9
32 9
42 144 , 10
48 4
55 3
57 11
60 5
67 7
75 4
75 9
Undifferentiated Pliocene and Miocene ContinuedSand, light-yellow-brown, medium- to fine-grained,
slightly clayey; contains indurated lumps of sand stone at top; lower contact sharp.
Sand, light-tan, medium- to fine-grained; contains trace of small indurated fragments.
Clay, light-gray to tan, very sandy to sandy; contains trace of white soft coarse sand-size phosphate.
Sand, light-gray, medium-grained, very clayey to clayey; contains trace of white soft cparse sand-size phosphate, and sparse sandstone fragments cemented by alum inum phosphate.
No recovery.Clay, green-gray, very slightly to slightly sandy, lami
nated; contains silicified(?) shell fragments, abundant. thin lenses of fine-grained sand, and abundant frag
ments of sandstone cemented by silica; lower contact sharp.
Sand, light-gray, very fine grained to medium grained at top, clayey to slightly clayey; contains abundant thin lenses of green very slightly sandy clay.
Clay, very slightly sandy (very fine grained), laminated with light-gray to pink fine-grained sand containing abundant heavy minerals.
Sand, light-gray, very fine grained, slightly clayey to clayey; interlenses with blue-green slightly sandy to
. very slightly sandy clay, containing trace of tan hardand soft very coarse sand-size phosphate at base.
Middle Miocene, Hawthorn formation:Clay, blue-green, very slightly sandy; contains sparse
laminae of fine-grained sand and trace of tan coarse sand-size phosphate at top.
Claystone, yellow- to olive-green; contains a few lenses of blue-green sandy clay, arid pellets of light-gray material, possibly phosphate; lower contact sharp.
Sand, tan, fine- to medium-grained, clayey; contains abundant lenses of gray-green very clayey, fine grained sand, and sparse black and tan very coarse sand- to granule-size phosphate; at 74 ft. 4 in. a few fragments of sandstone cemented by aluminum phosphate.
Sand, blue-green to olive-green, fine- to coarse-grained, .clayey to very clayey; contains large fragments of black and brown chert, and trace of black sand-size phosphate and silicified shell fragments at base.
G7, . 21. T. 28 S., K. 21 E., Hillsborough County, Fla. Elevation, 90 feet
0 05 0
17 2
5 017 2
27 6
Quaternary: - Not cored. Sand, gray to light-brown, slightly iron-stained, medium-
to fine-grained, very slightly to slightly clayey, locallyindurated; many intervals of no recovery.
Sand, white to light-gray-brown, medium-grained,slightly clayey in places; contains sparse thin lensesof light-blue sandy clay.
96 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
Depth
From (ft In)
T<(ft
> in)
Lithology
G7 Continued
27 6
40 9
44 11
58 9
107 1
110 9
128 1
131137
40 9
44 11
58 9
107 1
110 9
128 1
131 1
137 5150 5
Quaternary:Poor recovery; probably light-yellow-brown to violet-
brown and white, medium- to fine-grained very slightly clayey sand.
Poor recovery; probably gray-brown to violet-brown fine- to medium-grained very slightly clayey sand.
Sand, light-brown to gray, fine- to medium-grained, slightly clayey; contains trace of indurated fragments, and thin lenses of gray-blue clayey sand.
Sand, light-tan to gray and violet-brown, medium- to fine-grained, very slightly to slightly clayey; contains abundant indurated fragments, and, at base, brown to black carbonaceous material.
Wood, black and brown, carbonized, in.black medium- grained very slightly clayey sand.
Sand, black, medium-grained, very slightly clayey; many intervals of no recovery.
Sand, black to brown, medium-grained, slightly clayeyto clayey.
Undifferentiated Pliocene and Miocene:No recovery.Sand, brown to black, fine to very fine grained, very
clayey to clayey, laminated; contains organic ma terial, sparse brown pebble-size phosphate, and marca- site replacing phosphate and clay.
G8, SWJiSWJi sec. 8, T. 28 8., R. 21 E., Hillsborough County. Fla. .Elevation, 65 feet
0 0
10 9
12 914 0
15 6
20 1
27 6
10 9
12 9
14 015 6
20 1
27 6
33 11
Quaternary:No recovery.
Undifferentiated Pliocene and Miocene:Sand, very light gray, medium- to coarse-grained,
slightly clayey; contains trace of white clay, probably phosphatic.
No recovery.Sand, light-gray, medium- to fine-grained, slightly clayey
to clayey; contains sparse fragments of sandstone cemented by aluminum phosphate; lower contact sharp.
Clay, light-gray to green-gray, very slightly to very sandy (medium-grained); contains aluminum phos phate and sparse white soft very coarse sand- to granule-size phosphate.
Sand, very light gray to tan, fine to very fine grained, very clayey to clayey; contains aluminum phosphate and sparse white soft coarse sand- to granule-size phosphate.
Sand, white to very light gray, fine- to medium-grained, slightly clayey; contains sparse white soft sand-size phosphate.
LITHOLOGIC LOGS OF CORE HOLES 97
Depth
From (ft In)
To- .(ft. In)
Lithology
G 8 Continued
.33 11
38 11
41 5
43 0
46 0
47 2 47 . 5
48 . 3
50 0
51 6
51 10
38 11
41 5
43 0
46 0
47 2
47 548 , 3
50 0
51 6
Middle Miocene, Hawthorn formation:Clay, light-tan to gray, sandy to very sandy (fine- to
medium-grained); contains abundant fragments of white aluminum phosphate and light-brown sandy
.clay.Sand, light-gray, fine-grained, very clayey; contains
abundant fragments of aluminum phosphate.Sand,'light-gray to light-blue-gray, fine-grained, slightly
clayey; contains sparse sandstone fragments cemented by aluminum phosphate.
Sand, gray-green to gray-blue mottled, fine-grained, very clayey; contains sparse thin lenses of white, medium-grained sand.
Clay, pinkish-tan, very sandy, and sand, fine-grained, very clayey, slightly calcareous, interlaminated with green-gray sandy clay; lower contact sharp.1
Lower Miocene, Tampa limestone:Tripoli, white; contains Helisoma sp.Limestone, gray-blue, clayey, very sandy to sandy;
contains fragments of light-tan slightly calcareous clay..-
Limestone, light-tan to gray-green,' clayey;, contains trace of very fine-grained sand, and fragments of tan soft limestone, and, at base, claystone and sand stone, containing black to brown sand-size phosphate; lower contact sharp.!
Sand, light-gray, fine-grained, slightly clayey to clayey; contains abundant fragments of weathered limestone, and abundant black very fine grained sand; lower con tact sharp.
Clay, very light green gray and tan, slightly sandy to sandy; contains sparse thin lenses of white sand.
Sand, gray and streaked with yellow-brown, clayey to very clayey; contains abundant small fragments of
' tripoli and weathered limestone. .
G9. . 6, T. 28 S. ( R. 21 E., Hillsborough County, Fla. Elevation, 50 feet
0 05 5
10 117 7
21 9
23 9
5 510 1
17 721 9
23 9
.27 . 0
Quaternary:Not cored, no recovery.Sand, dark-brown to light-tan, finer to medium-grained,
slightly indurated, very slightly clayey. Undifferentiated Pliocene and Miocene:
Poor recovery; probably tan sand.Sand, brown-gray, medium- to fine-grained; contains at
base sparse fragments of sandstone cemented by aluminum phosphate.
Clay, gray to light-green-gray, very sandy to sandy, and very clayey sand; contains abundant small frag ments of hard phosphatic (?) clay, and sandstone cemented by aluminum phosphate.
Poor recovery; probably tan to gray-green fine-grained- slightly clayey sand.
50122* 59 8
98 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
- '" " Depth
From (ft in)
To-(ft in)
Lithology
27 028 .7
33 736, 9
38 5
43
48 1151 0
5253
'55 6
55 10
2833
3638
43
47
48 11
5152
5355
Middle Miocene, Hawthorn formation:Clay, gray-green, very slightly sandy to pure.Sand, light- to dark-gray-green, medium-grained, very
clayey, and very sandy clay, contains abundant frag ments of sandstone cemented by aluminum phosphate;
- ' lower contact sharp. Lower Miocene, Tampa limestone:
. Sand, tan, fine to very fine grained, very slightly clayey.Sand, light-gray-green, fine-grained, clayey to very
clayey; contains abundant thin lenses of white sand.Clay, gray to blue-gray and gray-green, slightly sandy
to pure; contains thin lenses of white very fine-grained sand, and abundant fragments of white tripoli with unidentifiable casts and molds of gastropod; lower contact sharp.
Clay, light-gray, sandy; contains lenses of gray-green pure clay, and very abundant fragments of tripoli, chalcedony, and weathered limestone; lower contact sharp.
Clay, blue-green; contains abundant fragments and lenses of soft slightly calcareous clay; lower contact sharp.
Clay, same as 43 ft. 1 in. to 47 ft. 7 in.Clay, blue-green to light-tan, slightly calcareous; con
tains abundant fragments of weathered limestone.No recovery; probably sand.Clay, light-gray to olive- and blue-green, very calcareous;
contains abundant fragments of soft limestone and thin clay seams.
No recovery; probably sand. Oligocene, Suwannee limestone:
Limestone, white to light-tan, and trace of sand; con tains at top, thin lenses and fragments of blue-green slightly calcareous clay; fossils, Sorites, Peneroplis, CMamys sp. cf. C. brooksvillensis Mansfield, and Kuphus incrassatus (Gabb).
GIO. . 7, T. 29 S., K. 21 E., Hillsborough County, Fla. Elevation, 60 feet
0 0
9 2
14 11
16 2
24 2
9 2
14 11
16 2
24 2
28 5
Quaternary:Not cored, no recovery..
Undifferentiated Pliocene and Miocene:Clay, light gray-green to gray, very to slightly sandy;
contains sparse to abundant white soft sand- topebble-size phosphate.
Clay, light-gray-green to white, very slightly sandy;contains very abundant white soft coarse sand-sizephosphate, and a few fragments of sandstone cementedby aluminum phosphate.
Middle Miocene, Hawthorn formation:Clay, yellow-green to light-blue-green, very sandy to
trace of sand in bottom; contains very thin lenses ofvery fine grained calcareous sand, and sparse whitesoft granule-size phosphate.
Clay, brown-green, very slightly sandy, laminated,,iron-stained.
..MTHOLOGIC LOGS OF -COKB? HOLES 99
Depth
From (ft in)
To (ft In)
-* - -- . .- ....« ,;....«........ .. ...,.. .. , ...,.,, ^^.^ ,.,....._. . .1
... ... Llthology ..-,-., .... . .,......,_. - -' - ' ',n£
; . , . ;'" -,
G10 -Continued
28 5
43 :l6
48 4
56 3
43 6
48 ; 4.
56 3
59 9
61 iO62 2
Middle Miocene, Hawthorn formation- ' Continued jClay, lightrgray-green to gray; very isandy, and, clayey
:>. . ;'. :sand; contains sparse-tan and black coarse :sand-size r ;, phosphate. . ; j ' Lower Miocene, Tampa limestone: I !
Sand, light-tan to very light gray-green, fine to-very fine . : .grained, heavily iron stained at top; lower contac.t
. ; ' sharp. / ..- . -.;. ! >. '. Sand, tah to gray,, very fine grained, very t6 slightly
, clayey, .and very.sandy clay; contains sparse frag- .. ments .of ,claystone and sandstone with black and
. brown coarse sand-size phosphate , locally cemented ...:by':silica; lower contact sharp. : : Sand, tan to gray, very fine grained,; very clayey, very
slightly calcareous; lower contact sharp." - - " Limestone, light tan, soft, slightly sandy, clayey.
Limestone, yellow-brown, sandy (fine-grained), clayey;, contains thin seams of sandy green and brown clay, and, at base, abundant brown : chert fragments; Charophyte oogonia (fresh-water plants). i
Gil, SEJiSEJi sec. 35,,T. 28 S., R. 20 E., Hillsborough County, Fla. . Elevation, 60 feet ' ;
0 0
9 6
13 1
18 1
21"": 8-22 7
28 6
33 10
35 1
9 6
13 1
18 1
22 728 6
33 10
35. 1
.36 . .1
Quaternary: -Poor'recovery; probably yellow-brown medium- to fine
grained very slightly clayey sand. Undifferentiated Pliocene and Miocene:
Sand; light-gray to yellow-brown, medium-; to fine grained, slightly clayey to clayey; contains; in lower half, abundant fragments of iron hardpan.
Sand,- light-gray to white, fine-grained, clayey, locally strong iron staining; contains sparse patches of white poorly indurated sand, cemented by phosphatic
' (?) clay. ; Clay, light-gray to tan, sandy to very sandy (very
fine grained), heavily streaked by iron staining; contains fragments of phosphatic (?) white claystone, and sparse white soft phosphate. :
No recovery. . ; Sand, light-gray to yellow-brown, ;fine to very fine
grained, top clayey to very clayey, bottom very slightly clayey, iron streaked; contains visible heavy minerals, sparse poorly indurated patches, of sand
cemented by clay and aluminum phosphate, and a thin zone of iron-stained black carbonaceous jnaterial; lower contact sharp. 7
Clay, light-gray to light-yellow, variegated, slightly ' sandy; contains thin streaks and patches of black carbonaceous material, and at base, a trace of white soft' coarse sand-size phosphate.
Middle Miocene, Hawthorn formation: .:Sand, light-gray to brown, fine-grained, clayey; contains
sparse thin'lenses of slightly clayey sand, and white slightly sandy clay and,a trace of dark-brown granule- size 'phosphate; -''. ;
.. Clay^lightrgray to white, slightly sandy. :
100 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
Depth
From (ft in)
To (ft In)
Llthology
Gil Continued
36 139 0
43 1
46 11
Lower Miocene, Tampa limestone:No recovery; probably sand.Clay, light-yellow-green, slightly sandy to sandy; con
tains abundant fragments of slightly sandy limestone, and sparse black granule-size phosphate; lower con tact sharp; Trigonocardid'sp.j Camerina sp., Sorites sp.
Sand, light-green to very light gray and white, fine grained, slightly clayey to clayey, slightly calcareous; Sorites sp. and coral fragments.
Sand, light-gray to white, fine-grained, slightly clayey to clayey, very calcareous, locally indurated; contains small barnacles, Bryozoa, crab fragments, and mol- lusk molds, none identifiable. :
G12, NEtfSE^ sec. 27, T. 28 S., K. 20 E., Hillsborough County, Fla. Elevation, 85 feet
0 0
5 0
6 10
17 1
19 6
21 7
25 3
28 3
5 0
6 10
. 1.1 8
15 1
17 1
19 6
21 7
25 3
28 3
30 5
Quaternary:Not cored.
Undifferentiated Pliocene and Miocene:Clay, gray, iron-streaked, laminated, very slightly to
slightly sandy; lower contact sharp.Sand, light-green-gray, very fine grained, clayey, inter-
laminated with gray-green to orange, very sandy clay; lower contact sharp.
" Sand, very light gray green to tan, fine-grained, and very sandy clay; contains abundant fragments of sand, lightly cemented by aluminum phosphate (?).
Clay, light-green-gray, slightly sandy to sandy, inter- laminated with tan medium-grained, clayey sand; contains sparse white and tan soft coarse sand-size phosphate, and local cementation by aluminum phos phate.
Middle Miocene, Hawthorn formation:Clay, light-gray-green, iron-streaked, fine- to medium-
grained, very sandy to sandy, laminated at top; con tains abundant patches of black, probably carbona ceous, material, and sparse small lenses of tan clayey sand, with traces of aluminum phosphate (?).
Sand, tan to brown, fine- to medium-grained, clayey to very clayey; contains abundant thin len?es of white sandy phpsphatic(?) clay, and a trace of black very coarse sand to granule-size phosphate.
Sand, tan to light-green-gray, fine- to medium-drained, at top laminated and iron-streaked; contains abundant heavy minerals, and twiglike fragments 6f amber silica, and silicified gastropod shell fragments; lower contact sharp and probably irregular.
Lower Miocene, Tampa limestone:Sand, light-gray-green to tan, fine-grained, very clayey,
and very sandy clay; contains, at top and base, abundant fragments of pure white limestone and visible heavy minerals.
Limestone, white, slightly sandy (fine-grained), slightly clayey, soft; contains sparse iragments of tan dense slightly sandy limestone.
LITHOLOGIC LOGS OF CORE HOLES 101
Depth
From (ft In)
To (ft In)
. . Lithology ' " " ~
G13, SEJiNEJi sec. 20, T. 23 S., R. 20 E., Hillsborough County, Fla. Elevation, 80 feet ....
0 0
8 6
14 0
21 021 9
22 11
37 2
42 544 5
51 0
8 6
14 Q
21 0
21 922 11
37 2
42 5
44 551 0
Quaternary: ;Poor recovery; probably brown fine-grained very
slightly clayey sand, containing abundant lumps of sand cemented by clay.
Undifferentiated Pliocene and Miocene:Sand, yellow- and orange-brown to light-gray, fine- to
medium-grained, clayey; contains fragments of sand stone cemented by clay.
Clay, light-green-gray to yellow-brown, trace to no sand; contains abundant fragments of sand cemented by aluminum phosphate^ and claystone.
No recovery.Sand, very light tan, fine-grained, clayey; contains thin
lenses of gray-green sandy clay, and sparse white soft coarse sand- to granule-size phosphate; lower contact sharp. ........ ..... . .
Middle Miocene, Hawthorn formation:Clay, gray-green to mottled orange, very slightly sandy;
contains "trace of sandstone'cemented by aluminum phosphate, and sparse laminae of clayey sand.
Lower Miocene, Tampa limestone:Sand, light-gray-green to mottled brown, fine- to me
dium-grained, clayey to very clayey; contains abun dant fragments of white, leached limestone, and tripoli, and a layer of dark-brown iron-cemented sand-
stone, and trace of fine sand-size phosphate(?).No recovery.Clay, .light-gray to very light green gray, sandy to very
sandy (very fine grained); contains layers of fragmentsof weathered limestone in sand, and abundant laminae
of very fine grained sand, and light-green noncalcare-ous clay, and, at base, layer of brown and white chert.
Limestone, white, slightly sandy (fine-grained), slightly clayey, soft; contains sparse grains brown carbonate; unidentifiable mollusks and Foraminifera.
0
514
27
28
30
0
07
9
10
1
5
1427
28
30
31
0
79
10
1
5
G14, NW&NWJi sec. 17, T. 28 S., R. 20 E., Hillsborough County, Fla. Elevation, 60 feet
Quaternary:Not cored.
" Undifferentiated Pliocene and Miocene:Poor recovery; probably tan to light-orange-brown sand. Sand, tan and gray to light-orange-brown, fine- to me
dium-grained, very slightly clayey to clayey. Clay, light-green-gray to very light orange, very slightly
sandy; contains sparse small patches of clayey iron- cemented sand. |
Sand, light-green-gray, very slightly to slightly clayey. Middle Miocene, Hawthorn 'formation: '
Clay, light-green-gray, patches and streaks of orange- and violet-brown and light-gray; abundant fragments of sandstone cemented by aluminum phosphate.
102 MIDDLE TERTIARY &OCK8 IN PART OF WEST-CENTRAL FLORIDA
Depth
From (ft in)
To- (ft In)
v.-v-;;r. Lithology
G14 Continued
31 5,
32 2
34 10
35 6
36 9
32 2
34 10
35 6
36 9
44 6
Lower Miocene, Tampa limestone:Sand, light-green-gray mottled with orange-brown,
medium- to fine-grained, very slightly clayey to clayey.Clay, light-gray-green and mottled orange-brown, very
sandy to sandy; contains sparse lenses of white fine grained sand, and abundant patches of white non- calcareous clay; lower contact sharp.
Sand, gray to orange brown, very slightly clayey; lower contact sharp. ^ .
Clay and sand as in 32 ft. 2 in. to 34 ft. 10 in,; lower contact sharp. i
Limestone, white to light-gray, slightly sandy; to sandy (fine-grained), slightly clayey, soft; contains fragments of white hard limestone, some partly silicified, and sparse thin lenses of white and brown sand. .
05.
.7
13
141616
17
.19
21
39
40
"46
48
00
1
10,g:
. 6"
8
5
,3
11
9
'9
11
0
57
13
14
161617
19
.21
'39
40
. 46
48
49;,
01
10
8
685.
3
.11
9
9
11
0
3,
G15, SWJiSWJi sec. 4, T. 30 S., R. 20 E., Hillsborough County, Fla. Elevation, 40 feet
Quaternary: Not cored.Sand, tan to white, medium- to fine-grained.
Undifferentiated Pliocene and Miocene: ' - Sand, light-gray to tan mottled with light-orange-brown,
very slightly clayey; '- Clay, gray, very slightly sandy; contains abundant small
lenses of white to light-gray sand with heavy minerals. ; No'recovery; '
Clay, as in 13 ft. 10 in. to 14 ft. 8 inj .Sand, light-gray to gray mottled orange-brown, very
slightly to slightly clayey; lower contact sharp, ir regular.
Clay, green, laminated with gray very slightly clayey sand; contains abundant fragments of sand- to cobble- size sandstone cemented by aluminum phosphate.
, _.. . Clay, very light gray, very slightly to..slightly sandy; contains abundant white hard coarse sand- to granule- size phosphate nodules.
Middle Miocene, Hawthorn formation:Sand, very light" gray, slightly iron-stained at base, very
slightly clayey; contains abundant white phosphate nodules, trace of black sand-size phosphate.
Clay, very light yellow, very sandy to sandy, slightlycalcareous; lower contact sharp. ] ' -..
Lower Miocene, Tampa limestone:Clay, dark-red-brown to light-yellow-brown, ; sandy to
very sandy, laminated; contains abundant fragments of red-brown to black hardpan. .'"' :
Clay, very light yellow, slightly iron stained, slightly to very sandy; contains a lens of light-green-gray clayey sand. _ .'/ . ' I ' \
- Limestone, white, .slightly sandy, hard, very <slightly - , clayey; Murex sp. .cf. M. trophbniforrhis < Heilprin,
."'; . Area irregularis, Cardiuw sp. cf. G. anclotense Mans field, Anomalocardia penita.
LITHOLOGIC LOGS OF CORE, HOLES 103
Depth
From (ft In)
To- Ut In)
Lithology
G16, SWJiSWJi sec. 18, T. 30 8., R. 20 E., Hillsborough County, Fla. Elevation, 25 feet
513
17
24
27 5
Quaternary: . : Not cored, no recovery. Poor recovery; probably tan to dark-brown very fine
to medium grained, very slightly clayey sand. Sand, tan to dark-gray-brown, fine-grained, slightly
iron-stained, very slightly to slightly clayey; lower contact sharp.
Undifferentiated Pliocene and Miocene:Clay, dark-gray-green, slightly sandy to sandy (very fine
grained), and olive-green to tan very fine grained slightly clayey calcareous sand; contains sparse to abundant tan and black soft sand- to granule-size phosphate nodules, heavy minerals, and sparse fragments of very light tan limestone; lower contact sharp.
Middle Miocene, Hawthorn formation:Limestone, light-tan, very slightly sandy (fine- to medium-
grained), very clayey, dolomitic (?); contains abund ant lenses of gray calcareous clay, and sparse granule- and pebble-size phosphate nodules; large Ostrea sp and other mollusk fragments.
G17, NWJiSEJi sec. 13, T. 30 8., R. 19 E., Hillsborough County, Fla. Elevation, 25 feet
0 05 0
9 7
20 5
21 5
26 0
5 09 7
20 5
21 5
26 0
28 7
40 9
Quaternary: Not cored. ;Sand, light-brown at top, white in middle, light-gray at
base, medium- to fine-grained.Sand, light-gray-brown to dark-gray, very fine to fine
grained, very slightly clayey; contains black clayey organic material.
Clay, black, very slightly sandy; contains organicmaterial.
Undifferentiated Pliocene and Miocene:Clay, dark-gray to light-gray-brown, slightly sandy;
contains sparse fragments of leached soft limestone, and sparse tan hard sand- to pebble-size phosphate nodules.
Clay, dark-gray-green to light-tan, slightly sandy, cal careous along partings; contains, at base, green-gray clay with marcasite along fractures; lower contact sharp.
Clay, dark-gray-green, slightly sandy to sandy (fine grained), with .abundant lenses of olive-green to tan very fine grained calcareous sand, contains sparse black and tan sand- to granule-size phosphate nodules, abundant heavy minerals, and sparse fragments of very light tan rounded limestone; lower contact sharp.
104 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
Depth
From ,(ft In)
To (ft In)
Lithology
G17 Continued
4041
45
4145
48
Lower Miocene, Tampa limestone: ;No recovery; probably sand.Clay, light-green-gray to light-tan, sandy to very sandy,
slightly calcareous; contains sparse fragments of poorly indurated sand cemented by clay, sparse small frag ments of gray chert, sparse black and brown hard pebble-size phosphate nodules, and abundant heavy minerals.
Limestone, very light tan, sandy (fine-grained), slightly clayey, soft; contains a trace of fine sand-size phos phate nodules; Sorites sp.
G115, . 31, T. 27 S. ( R. 24 E., Polk County, Fla. Elevation, 140 feet
0 04 0
5 7
12 1014 8
23 0
31 0
36 137 10
12 10
14 823 0
31 0
36 1
Quaternary: Not cored.Sand, tan to dark-brown, fine-grained.
Undifferentiated Pliocene and Miocene:Sand, light-gray to white, fine-grained, very slightly
clayey. No recovery. Sand, light-gray to light-brown, medium-grained, no
clay to slightly clayey. Middle Miocene, Hawthorn formation:
Sand, gray to white, medium-grained, clayey; containssparse tan white sand- to pebble-size phosphate.
Clay, light- to dark-brown, slightly sandy (medium- .grained), slightly calcareous; contains sparse brown, white sand- to pebble-size phosphate.
Lower Miocene, Tampa limestone: No recovery.Clay, light- to dark-brown, slightly sandy (fine- to
coarse-grained), locally very calcareous; contains sparse brown, white sand- to pebble-size phosphate.
G105, S^ sec. 18, T. 27 S., R. 24 E., Polk County, Fla. Elevation, 170 feet
0 05 0
8 0
9 014 0
15 0
34 0
37 0
5 08 0
9 0
14 015 0
34 0
37 0
41 0
Quaternary: Not cored.Sand, light-brown, medium-grained.
Undifferentiated Pliocene and Miocene:Sand, light-brown and gray, mottled, medium-grained,
slightly clayey to clayey. No recovery; probably loose sand. Sand, tan and gray, mottled, fine- to medium-grained,
slightly clayey. Poor recovery; sand, gray to brown and gray,, mottled,
fine- to medium-grained, very slightly to slightly clayey. Middle Miocene, Hawthorn formation:
Clay, brown to green-gray, trace of very fine grainedsand.
Sand, green-gray, medium- to coarse-grained, veryclayey; contains tan medium to coarse sand-sizephosphate.
105
Depth
From (ft In)
To-(ft In)
, ' : , Lithology
G105 Continued
41 0
: 43 0
43 10. 45 0
] 46 647 7
"48 6
52 0
43
43
45 46
4748
52
52
0 0.40
20 0
22 0
29 0
31 0
41 0
:43. 0
: 43 9
420
22.
29
31
41
43
43
43
0 0
72
12 014 3
.15 8
.21 4
7
12
141521
.22
0
10
0-6
76
0
10
.Middle Miocene,- Hawthorn, formation ContinuedClay, gray, slightly sandy . (medium-grained) ; contains
sparse sand-size phosphate.Sand, brown, medium- to coarse-grained, clayey; contains
sparse, brown medium to coarse sand-size phosphate.No recovery.
Clay, green-gray, sandy (medium-grained); contains: dark-brown to tan sand- to pebble-size phosphate.
No recovery. . vSand, green-gray, medium to very coarse grained, very
clayey, slightly calcareous; contains black, brownmedium to very coarse sand-she phosphate:
Clay, tan, very sandy (medium-grained), very calcareous;contains sparse, black, brown medium to very coarsesand-size phosphate.
' Limestone, white, very sandy (medium-rgrained), soft,contains sparse, 'black, brown medium to verycoarse sand-size phosphate. "
G106, WW sec. 1, T. 27 S., R. 23 E., Polk County, Fla.Elevation, 135 feet
00
0
0
0
0
0
9
10
Quaternary:. Not cored.Sand, tan, brown to black, gray, medium- to fine
grained, clayey.No recovery; probably loose sand.
Middle Miocene, Hawthorn formation:Sand, green to green-gray, fine- to medium-grained,
clayey to very clayey; contains tan, sand- to pebble-. size phosphate.
Clay, green, sandy (fine-grained); contains sparse tansand- to pebble-size phosphate.
Lower Miocene, Tampa limestone:Clay, green to dark-green, very slightly to very sandy
(very fine grained) ; contains trace of tan phosphate.Clay, dark-green, very slightly sandy (very fine grained) ;
contains black chert.Sand, green-gray, very fine to fine-grained, very clayey,
slightly calcareous.Limestone, white, very slightly sandy, soft.
G107, NWJiSE X sec.,27, T. 26 S., R. 23 E., Polk County, Fla. . - Elevation, 120 feet
2
0
384
4
Quaternary:Not cored; no recovery.
Middle Miocene, Hawthorn formation:Poor recovery; partly dark-gray medium-grained clayey
sand.Sand, blue-gray, medium-grained, clayey.
. No recovery.Clay, blue to green-brown, very slightly sandy; contains
abundant chert.Sand, green-gray, fine- to medium-grained,' clayey to
very clayey; lower contact sharp.
106 MIDDLE TERTIARY ROCKS IN PART -OF WEST-CENTRAL FLORIDA
Depth
From (ft In)
To- (ft In)
Lltbology
G107 Continued
222326
2831
232628
3133
Lower Miocene, Tampa limestone:Clay, blue, very slightly sandy.No recovery.Clay, blue, very slightly to slightly sandy (fine-grained) ;<'
contains sparse chert.No recovery.Clay, blue-green, slightly sandy (very fine grained) f
slightly calcareous; contains chert; Terebra sp., Knefas- tia sp. aff. K. brooksvillensis Mansfield, Olivella sp. cf. 0. posti Dall, Turritella atacta Dall, Architectonics n. sp.?, Anadara latidentata (Dall), Chlamys sp., Cardium delphicum Dall, Callocardia sp., Pitar sp., Venus sp., Corbula sp.
G108, SWJi sec. 8, T. 26 S., R. 23 E., Polk County, Fla. Elevation, 100 feet
Quaternary:Not cored.
Middle Miocene, Hawthorn formation: . .Sand, gray to brown, mottled, medium-grained, very
clayey.Sand, white to green-gray, fine- to coarse-grained, very
clayey; contains fragments of white sandstone ce mented by silica and aluminum phosphate (?).
Sand, tan, medium-grained, slightly clayey. Lower Miocene, Tampa limestone:
No recovery.Sand, green-gray, fine-grained, very clayey.Clay, green-brown, sandy to very sandy; contains
sparse chert.No recovery.Sand, green-gray, fine-grained, slightly to very slightly
clayey. Oligocene, Suwannee limestone:
Limestone, white, very slightly sandy, soft; Turritella halensis Dall, Glycymeris suwannensis Mansfield, Divaricella sp., Pitar sp., Corbula sp., Myrtaea sp. cf. M. taylorensis Mansfield, Eucrassatella sp. cf. E. paramesus Dall, Chlamys sp. cf. C. brooksvillensis Mansfield, Orthaulax hernandoensis Mansfield, Am- auropsisl sp., Phacoides sp., Chione sp. cf. C. bain- bridgensis Dall, Chione sp., Pitar sp. cf. P. heilprini Mansfield, Anatina sp., Venus sp. ... . .
0
4
6
9
101214
1517
19
0
0
0
6
200
80
4
4
6
9
10
121415
1719
44
0
0
6
2
008
04
8
G109. NWJiNWJi sec. 1, T. 26 S., R..22 E., Polk County, Fla. Elevation, 95 feet
0 0
4 0
'6 10
4 0
6 10
9 0
Quaternary:Not cored.
Middle Miocene, Hawthorn formation:Sand, gray to brown, mottled, medium-grained, clayey
to very clayey. . Clay, sandy to very sandy (medium-grained); contain/*
siliceous concretions.
Depth
Fro(ft
m In)
T((ft
> in)
; '' ''Lithology i
; . - / .
G109 Continued
9
12.
151617
0
.6,
360
12
15
161726
6
3
604
Lower Miocene, Tampa limesone:Sand, green-gray, fine-grained, clayey to very clayey;
contains siliceous fragments. ; Clay, gray, slightly sandy (fine-grained).
Oligocene, Suwannee limestone: ; ;No recovery.Sand, fine-grained, clayey. . :Limestone, white, soft; Tfitiaria n sp.?, Venus sp.,
Bryozoa, Barnea sp., ; Coskinolina floridana, Ostracods^
G110, . 27, T. 25 S., R. 22 E., Pasco County, Fla. Elevation, 85 feet
, o 47
,1014
0
00
00
4
.' 710
1419
0
00
06
Quaternary:. Not cored. . . .
Lower Miocene, Tampa limestone.. .Clay, gray, very sandy. . .
Sand, gray to tan, fine- to medium-giOligocene, Suwannee limestone:
,No recovery. -Chert, white.
....!-
rained, clayey.
Gill, r 20, T. 25 S., R. 22 E., Pasco County, Fla. Elevation, 140 feet
0 0
4 0
13 0
21 064 5
65 571 573- 0
91 '6
95. 5.96 3,99- 0
LOO 0
4
13
21
6465
717391
95
9699
100101
101
Quaternary: :Not cored. ; ,
Middle Miocene, Hawthorn formation: ;Poor recovery; partly red-brown fine-'to medium-grained.
very slightly clayey sand. : ' ; Sand, tan and gray, mottled, fine- to medium-grained,.
clayey: ' Sand, white, fine-grained, very slightly clayey to clayey. Sand, brown, medium-grained, very clayey ;> contains
abundant fragments of sandstone cemented by aluminum phosphate. f
Lower Miocene, Tamp'a limestone: ;Clay, yellow-brown, very slightly; sandy. , Sand, brown, fine- to medium-grained, very clayey. Poor recovery; partly gray and brown mottled fine
grained clayey to very clayey sand, containing sparse , fragments of sandstone .cemented by aluminum.
; -. ' phosphate. ' ' ; '. .'Clay,' yellow-brown arid black, mottled, very slightly
sandy, to very sandy. i Clay,, white, slightly sandy, phosphate. .',
Clay, brown, slightly sandy '. i .Clay, white, slightly sandy, hard, phosphatic. ; > - ; Clay, tan to gray, white, banded, vefy sandy.',
Oligocehe, Suwannee limestone: "Limestone, white and tan, mottled, slightly sandy,,
clayey, soft.
108 MIDDLE TERTIARY ROCKS IN PART OF WEST-CENTRAL FLORIDA
Depth
From (ft In)
T(ft
> In)
. . . Lithology
G112, SEJi sec. 13, T. 25 S., R. 21 E., Pasco County, Fla. ... . .. Elevation,'140-feet ...........
Quaternary:Not cored.
Middle Miocene, Hawthorn formation:Sand, dark-red-brown, fine- to medium-grained, slightly
clayey.Sand, brown, fine- to medium-grained, clayey; contains
fragments of sandstone cemented by aluminum phos phate. .
Sand, brown, gray, mottled and banded, fine- to medium- grained.
Lower Miocene, Tampa limestone:Clay, green-gray, very slightly to very sandy (fine
grained).Sand,.light gray to light-green-gray, fine-grained, very
slightly clayey to clayey.Clay, green-gray, white, brown, very slightly sandy to
sandy (fine- to medium-grained), phosphatic.Clay, brown to white, slightly to very sandy, phosphatic;
Glycymerissp. Oligocene, Suwannee limestone:
Limestone, white, very slightly sandy (very fine grained), soft; Peneroplis' sp., Asterigerina subacula floridensis.
G113, NEJi sec. 14, T. 25 S., R. 21 E., Pasco County, Fla. Elevation, 185 feet
0
4
18
22
30
48
52
61
67
0
0
6
4
5
0
9
0
0
4
18
22
30
48
52
61
67
67
0
6
4
5
0
9
0
0
11
0
4
68 78
SO 82
87
89
105 111
114
0
0
0 0
0 5
0
0
0 0
6
4
68
78 80
82 87
89
105
111 114
116
Quaternary:Not cored.
Middle Miocene, Hawthorn formation:Sand, dark-brown to light-gray, mottled, fine- to med
ium-grained, very slightly to very clayey.No recovery; probably loose sand.Clay, brown, very sandy (medium- to coarse-grained);
contains fragments of sandstone cemented by alumi num phosphate.
Clay, brown, very slightly sandy.Clay, brown, sandy ((medium- to coarse-grained); con
tains abundant white, tan sand- to pebble-size phos phate nodules, and fragments of sandstone cemented by aluminum phosphate.
Sand, brown to -black, fine- to medium-grained, veryclayey.
Lower Miocene, Tampa limestone:Sand, tan to light-gray, mottled, fine-grained, very
clayey.No recovery.Clay, green-gray to brown and white, very sandy,
phosphatic.Clay, white, slightly sandy (fine-grained), hard, brittle,
phosphatic, encrusted with secondary phosphate.
LITHOLOGIC LOGS OF CORE HOLES 109
Depth
Fro(ft
m In)
T((ft
> In)
Llthology
G 113 Continued
116134
138
0
41123
25
26
19
7
134138
144
0
06
6
8
0
4
1123
25
26
30
97
3
Oligocene, Suwannee limestone:No recovery.Poor recovery; partly green-gray and brown very sandy
clay.Poor recovery; partly white slightly sandy (very fine
grained) limestone; Sorites sp^, Asterigerina subdculafloridensis, calcareous algae.
GJ14, NEJi sec. 22, T. 24 S., E. 21 E., Pascp. County, Fla.Elevation, 85 feet
0
66
8
0
0
Quaternary:Not cored.
Lower Miocene, Tampa limestone:Sand, white, fine-grained, clayey.Clay, green-gray, brown, mottled, very sandy to sandy
(fine-grained) .Clay, white, brown, mottled, sandy (fine-grained), phos-
phatic; contains chert and secondary phosphate crusts. Limestone, white, tan, slightly sandy (fine-grained), soft,
phosphatic. Oligocene, Suwannee limestone:
Limestone, tan, slightly sandy (fine-grained), slightlyphosphatic; Sorites sp., calcareous algae.
PageAcknowledgments 6 Ages. See individual formation names.
Bone Valley formation, age 48-49 lithology..... 49weathering_ .. 49
Chemical analyses.._.... ----- 31,39,48,53Chert, secondary...___........ 11,30-31,50-51,55Clay, mineralogy... - 32,52Core holes, logs- .. . .. - ... 91-109
Dolomite deposits, economic value.. . 68 Drainage. 4-5
Fault, Polk County____._ ._----- 59-60Fossils, Hawthorn formation_. . 36,37-38
Ocala limestone. 9Suwannee limestone 11,12-13Tampa limestone. .__... 24,26-29
Hawthorn formation, age and extent..... 33-34exposures, general.. 36
Hillsborough County.. . . 82-85 Manatee County.... 90Pasco County. _ ... 85-86 Polk County. ... ... 86-89 Sarasota County ... .... 90
fossils..... 36,37-38geologic history, summary. ... 67 lithology.... . 34-35petrographic details_. 15,
16,17,19,20,36,39-48,66,57 previous work 33 sedimentation.. 64-65 stratigraphicrelations.... ------- 35-36,60-62weathering... - 54-55
Investigations, present, purpose.. 2-4 previous 4 See also individual formation names.
Laboratory work, evaluation of results 7-8procedures...- 6-7
Land-pebble phosphate district, location..... 3Limestone deposits, economic value.... 68-69
Ocala limestone, age and extent...... 8fossils^___-_______..----__... 9,60lithology, general. ... . ----- 8-9petrographic details... 19,57 previous work 8 stratigraphic relations . . 9
Ocala uplift, geologic history.... 58-59
PagePetrographic details. See individual forma
tion names.Phosphate, in the Hawthorn limestone 36,
39,41,54-55in the Tampa limestone... . 32,54,68
Phosphate deposits, economic value.. 67-68Post-middle Miocene rocks, lithology.- 48-50
petrographic details. _ . ... 67weathering_ . _ 65See also Bone Valley formation.
Sand and clay of the Miocene, sedimentation. 65-66 Spectrographic analyses.... ..... ... 48Stratigraphic relations. See individual forma
tion names.Stratigraphic sections, Hawthorn formation... 40,
43,44 Structural features, remnants of Miocene clay
and sand.....__________ 62-63Suwannee limestone, age and extent.. _ 9-10
exposures, general..___________ nHillsborough County________ 72Pasco County....__________ 72-74Polk County_______.____ 75
fossils 11,12-13,60geologic history, summary.________ 66 lithology, general. __________ 10 petrographic details..__________ 11,
13-14,15,16,17,19,20,56,57 previous work....____________ 9sedimentation..... __________ 63stratigraphic relations...._______ 10weathering.... ____..____ 51
Tampa limestone, age and extent___ ___ 20-21exposures, general..___________ 24
Hillsborough County.__._._._ 75-79Pasco County____. ________ 79-80Pinellas County.__...._______ 80-81Polk County_____. _______ 80Sumter County...__________ 82
fossils _ ...__.. 24,26-29geologic history, summary ___ _____ 66-67lithology. . 21,22-23petrographic details..__________ 15,
16,17,19, 20,23,24-25,30-33,56,67 previous work_______________ 14-15 sedimentation_______________ 63-64 stratigraphic relations. ________ 21,60-62 weathering...._____________ 51-54
Temperature_________________ 4 Topography.. ___________ 4
Uranium deposits, economic value______ 67-68
Weathering. See individual formation names. Weathering periods, age____________ 55-50
o111